United States Postal Service

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https://en.wikipedia.org/wiki/United_States_Postal_Service 

United States Postal Service

Corporate signature used since 1993
USPS Headquarters
Agency overview
Formed	July 1, 1971; 49 years ago Washington, D.C., U.S.
Type	Independent
Headquarters	475 L'Enfant Plaza SW Washington, D.C. 20260-0004 U.S.
Employees	633,108 (496,934 career personnel, 136,174 non-career personnel) as of 2019
Agency executives	Louis DeJoy, Postmaster General Vacant, Deputy Post Master General Robert M. Duncan, Chairman of the Board of Governors
Key document	Postal Clause of the United States Constitution
Website	www.usps.com
Revenue (2019) US$ 71.1 billion Net income (loss) (2019) US$ (8.81 billion)

The full eagle logo, used in various versions from 1970 to 1993

The United States Postal Service (USPS; also known as the Post Office, U.S. Mail, or Postal Service) is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the United States, including its insular areas and associated states. It is one of the few government agencies explicitly authorized by the United States Constitution.

The USPS traces its roots to 1775 during the Second Continental Congress, when Benjamin Franklin was appointed the first postmaster general. The Post Office Department was created in 1792 with the passage of the Postal Service Act. It was elevated to a cabinet-level department in 1872, and was transformed by the Postal Reorganization Act of 1970 into the United States Postal Service as an independent agency. Since the early 1980s, many direct tax subsidies to the USPS (with the exception of subsidies for costs associated with disabled and overseas voters) have been reduced or eliminated.

The USPS, as of 2019, has 469,934 career employees and 136,174 non-career employees. The Postal Service is legally obligated to serve all Americans, regardless of geography, at uniform price and quality. The Post Office has exclusive access to letter boxes marked "U.S. Mail" and personal letterboxes in the United States, but has to compete against private package delivery services, such as United Parcel Service, FedEx, and Amazon.

History

On March 18, 1970, postal workers in New York City—upset over low wages and poor working conditions, and emboldened by the Civil Rights Movement—organized a strike against the United States government. The strike initially involved postal workers in only New York City, but it eventually gained support of over 210,000 United States Post Office Department workers across the nation. While the strike ended without any concessions from the Federal government, it did ultimately allow for postal worker unions and the government to negotiate a contract which gave the unions most of what they wanted, as well as the signing of the Postal Reorganization Act by President Richard Nixon on August 12, 1970. The act replaced the cabinet-level Post Office Department with a new federal agency, the United States Postal Service, and took effect on July 1, 1971.

Since the 1990s, Republicans have been discussing the idea of privatizing the U.S. Postal Service. The Donald Trump administration proposed turning USPS into "a private postal operator" as part of a June 2018 governmental reorganization plan, although there was strong bipartisan opposition to the idea in Congress.

Current operations

USPS delivery truck

https://en.wikipedia.org/wiki/United_States_Postal_Service

The United States Postal Service employs 633,188 workers, making it the third-largest civilian employer in the United States behind the federal government and Walmart. In a 2006 U.S. Supreme Court decision, the Court noted: "Each day, according to the Government's submissions here, the United States Postal Service delivers some 660 million pieces of mail to as many as 142 million delivery points." As of 2017, the USPS operates 30,825 post offices and locations in the U.S., and delivers 149.5 billion pieces of mail annually.

The USPS operates one of the largest civilian vehicle fleets in the world, with an estimated 227,896 vehicles, the majority of which are the easily identified Chevrolet/Grumman LLV (long-life vehicle), and the newer Ford/Utilimaster FFV (flex-fuel vehicle), originally also referred to as the CRV (carrier route vehicle). Made from 1987 to 1994 and with no air conditioning, no airbags, no anti-lock brakes, and lacking space for the large modern volume of e-commerce packages, the Grumman fleet ended its expected lifespan in fiscal year 2017. The replacement process began in 2015, and prototypes have been produced by various bidders, but due to delays as of May 2020, a final contract for replacement trucks has not been awarded.

It is by geography and volume the globe's largest postal system, delivering 47% of the world's mail. For every penny increase in the national average price of gasoline, the USPS spends an extra US$8 million per year to fuel its fleet.

A Grumman LLV, the USPS’ main type of delivery truck

The number of gallons of fuel used in 2009 was 444 million, at a cost of US$1.1 billion. The fleet is notable in that many of its vehicles are right-hand drive, an arrangement intended to give drivers the easiest access to roadside mailboxes. Some rural letter carriers use personal vehicles. All contractors use personal vehicles. Standard postal-owned vehicles do not have license plates. These vehicles are identified by a seven-digit number displayed on the front and rear.

A fleet of post office vehicles at the James Griffith Station in Spring Branch, Houston

The Department of Defense and the USPS jointly operate a postal system to deliver mail for the military; this is known as the Army Post Office (for Army and Air Force postal facilities) and the Fleet Post Office (for Navy, Marine Corps, and Coast Guard postal facilities).

In February 2013, the Postal Service announced that on Saturdays it would only deliver packages, mail-order medicines, Priority Mail, and Express Mail, effective August 10, 2013. However, this change was reversed by federal law in the Consolidated and Further Continuing Appropriations Act, 2013. They now deliver packages on Sunday—only for Amazon.com — meaning that carriers make parcel deliveries seven days a week. During the four weeks preceding Christmas since 2013, packages from all mail classes and senders were delivered on Sunday in some areas.

Parcels are also delivered on holidays, with the exception of Thanksgiving and Christmas.

The period between Thanksgiving and Christmas is the busiest time of the year for the USPS with the agency delivering an estimated 900 million packages during the period of 2018.

In May 2019, the Postal Service announced that it will be releasing a pilot of self-driving trucks to haul mail across the U.S. The 18-wheelers were developed by startup company, TuSimple. The pilot will last two weeks, making five total round trips to cities across the country.

In early May 2020, the USPS's board of governors confirmed that Louis DeJoy would be the new postmaster general.

Operation and budget

In 2016, the Postal Service collected $71.5 billion in revenue.

Revenue decline and planned cuts

In 2016, the USPS had its fifth straight annual operating loss, in the amount of $5.6 billion, of which $5.8 billion was the accrual of unpaid mandatory retiree health payments.

Declining mail volume

First-class mail volume peaked in 2001, declining by 43% as of 2017 due to the increasing use of email and the World Wide Web for correspondence and business transactions.

Private courier services, such as FedEx and United Parcel Service (UPS), directly compete with USPS for the delivery of urgent letters and packages. 

Lower volume means lower revenues to support the fixed commitment to deliver to every address once a day, six days a week. According to an official report on November 15, 2012, the U.S. Postal Service lost $15.9 billion its 2012 fiscal year.

Internal streamlining and delivery slowdown

In response, the USPS has increased productivity each year from 2000 to 2007, through increased automation, route re-optimization, and facility consolidation. Despite these efforts, the organization saw an $8.5 billion budget shortfall in 2010, and was losing money at a rate of about $3 billion per quarter in 2011.

On December 5, 2011, the USPS announced it would close more than half of its mail processing centers, eliminate 28,000 jobs and reduce overnight delivery of First-Class Mail. This will close down 252 of its 461 processing centers. (At peak mail volume in 2006, the USPS operated 673 facilities.) As of May 2012, the plan was to start the first round of consolidation in summer 2012, pause from September to December, and begin a second round in February 2014; 80% of first-class mail would still be delivered overnight through the end of 2013. New delivery standards were issued in January 2015, and the majority of single-piece (not presorted) first-class mail is now being delivered in two days instead of one. Large commercial mailers can still have first-class mail delivered overnight if delivered directly to a processing center in the early morning, though as of 2014 this represented only 11% of first-class mail. Unsorted first-class mail will continue to be delivered anywhere in the contiguous United States within three days.

Post office closures

In July 2011, the USPS announced a plan to close about 3,700 small post offices. Various representatives in Congress protested, and the Senate passed a bill that would have kept open all post offices farther than 10 miles (16 km) from the next office. In May 2012, the service announced it had modified its plan. Instead, rural post offices would remain open with reduced retail hours (some as little as two hours per day) unless there was a community preference for a different option. In a survey of rural customers, 54% preferred the new plan of retaining rural post offices with reduced hours, 20% preferred the "Village Post Office" replacement (where a nearby private retail store would provide basic mail services with expanded hours), 15% preferred merger with another Post Office, and 11% preferred expanded rural delivery services. Approximately 40% of postal revenue already comes from online purchases or private retail partners including Walmart, Staples, Office Depot, Walgreens, Sam's Club, Costco, and grocery stores. The National Labor Relations Board agreed to hear the American Postal Workers Union's arguments that these counters should be manned by postal employees who earn far more and have "a generous package of health and retirement benefits".

Elimination of Saturday delivery averted

On January 28, 2009, Postmaster General John E. Potter testified before the Senate that, if the Postal Service could not readjust its payment toward the contractually funding earned employee retiree health benefits, as mandated by the Postal Accountability & Enhancement Act of 2006, the USPS would be forced to consider cutting delivery to five days per week during June, July, and August.

H.R. 22, addressing this issue, passed the House of Representatives and Senate and was signed into law on September 30, 2009. However, Postmaster General Potter continued to advance plans to eliminate Saturday mail delivery.

On June 10, 2009, the National Rural Letter Carriers' Association (NRLCA) was contacted for its input on the USPS's current study of the effect of five-day delivery along with developing an implementation plan for a five-day service plan. A team of Postal Service headquarters executives and staff has been given a time frame of sixty days to complete the study. The current concept examines the effect of five-day delivery with no business or collections on Saturday, with Post Offices with current Saturday hours remaining open.

On Thursday, April 15, 2010, the House Committee on Oversight and Government Reform held a hearing to examine the status of the Postal Service and recent reports on short and long-term strategies for the financial viability and stability of the USPS entitled "Continuing to Deliver: An Examination of the Postal Service's Current Financial Crisis and its Future Viability". At which, PMG Potter testified that by the year 2020, the USPS cumulative losses could exceed $238 billion, and that mail volume could drop 15 percent from 2009.

In February 2013, the USPS announced that in order to save about $2 billion per year, Saturday delivery service would be discontinued except for packages, mail-order medicines, Priority Mail, Express Mail, and mail delivered to Post Office boxes, beginning August 10, 2013. However, the Consolidated and Further Continuing Appropriations Act, 2013, passed in March, reversed the cuts to Saturday delivery.

Retirement funding and payment defaults

The Postal Accountability and Enhancement Act of 2006 (PAEA) obligates the USPS to fund the present value of earned retirement obligations (essentially past promises which have not yet come due) within a ten-year time span. In contrast, private businesses in the United States have no legal obligation to pay for retirement costs at promise-time rather than retirement-time, but about one quarter do.

The Office of Personnel Management (OPM) is the main bureaucratic organization responsible for the human resources aspect of many federal agencies and their employees. The PAEA created the Postal Service Retiree Health Benefit Fund (PSRHB) after Congress removed the Postal Service contribution to the Civil Service Retirement System (CSRS). Most other employees that contribute to the CSRS have 7% deducted from their wages. Currently all new employees contribute into Federal Employee Retirement System (FERS) once they become a full-time regular employees.

On September 30, 2014, the USPS failed to make a $5.7 billion payment on this debt, the fourth such default.

On February 5, 2020, the House passed The USPS Fairness Act (H.R. 2382) with 309 Yeas and 106 Nays meeting the 2/3rd rule. The measure eliminates the requirement going forward and forgives all payments on which USPS has defaulted. It was moved to the Senate on February 10, 2020 and is awaiting action by senators.

Rate increases

Congress has limited rate increases for First-Class Mail to the cost of inflation, unless approved by the Postal Regulatory Commission. A three-cent surcharge above inflation increased the 1 oz (28 g) rate to 49¢ in January 2014, but this was approved by the commission for two years only. As of January 2019, first-class postage for up to 1 ounce is $0.55.

Reform proposals and delivery changes

Comprehensive reform packages considered in the 113th Congress include S.1486 and H.R.2748. These include the efficiency measure, supported by Postmaster General Patrick Donahoe of ending door-to-door delivery of mail for some or most of the 35 million addresses that currently receive it, replacing that with either curbside boxes or nearby "cluster boxes". This would save $4.5 billion per year out of the $30 billion delivery budget; door-to-door city delivery costs annually on average $353 per stop, curbside $224, and cluster box $160 (and for rural delivery, $278, $176, and $126, respectively).

S.1486, also with the support of Postmaster Donahoe, would also allow the USPS to ship alcohol in compliance with state law, from manufacturers to recipients with ID to show they are over 21. This is projected to raise approximately $50 million per year. (Shipping alcoholic beverages is currently illegal under 18 U.S.C. § 1716(f).)

In 2014, the Postal Service was requesting reforms to workers' compensation, moving from a pension to defined contribution retirement savings plan, and paying senior retiree health care costs out of Medicare funds, as is done for private-sector workers.

As part of a June 2018 governmental reorganization plan, the Donald Trump administration proposed turning USPS into "a private postal operator" which could save costs through measures like delivering mail fewer days per week, or delivering to central locations instead of door to door. There was strong bipartisan opposition to the idea in Congress.

In April 2020 Congress approved a $10 billion loan from the Treasury to the post office. According to the Washington Post, officials under Treasury Secretary Steven Mnuchin suggested using the loan as leverage to give the Treasury Department more influence on USPS operations, including making them raise their charges for package deliveries, a change long sought by President Trump.

In May 2020 Louis DeJoy was appointed Postmaster General and immediately began taking measures to reduce costs, such as banning overtime and extra trips to deliver mail. While DeJoy admitted that these measures were causing delays in mail delivery, he said they would eventually improve service. More than 600 high-speed mail sorting machines were dismantled and removed from postal facilities without explanation, raising concerns that mailed ballots for the November 3 election might not reach election offices on time. Mail collection boxes were removed from the streets in many cities; after photos of boxes being removed were spread on social media, a postal service spokesman said they were being moved to higher traffic areas but that the removals would stop until after the election. The inspector general for the postal service has opened an investigation into recent changes.

Coronavirus pandemic and voting by mail

Voting by mail has become an increasingly common practice in the United States, with 25% of voters nationwide mailing their ballots in 2016 and 2018. The coronavirus pandemic of 2020 has been predicted to cause a large increase in mail voting because of the possible danger of congregating at polling places. For the 2020 election, a state-by-state analysis concluded that 76% of Americans are eligible to vote by mail in 2020, a record number. The analysis predicted that 80 million ballots could be cast by mail in 2020 - more than double the number in 2016. The Postal Service sent a letter to 46 states in July 2020, warning that the service might not be able to meet the state's deadlines for requesting and casting last-minute absentee ballots.

The House of Representatives voted to include an emergency grant of $25 billion to the post office to facilitate the predicted flood of mail ballots. Trump conceded that the post office would need additional funds to handle the additional mail-in voting, but said he would oppose any additional funding so that "universal mail-in voting" would not be possible. On August 14, 2020, President Trump says he's willing to approve USPS funding if concessions are made to some funding asks in coronavirus relief package.

Governance and organization

The Board of Governors of the United States Postal Service sets policy, procedure, and postal rates for services rendered. It has a similar role to a corporate board of directors. Of the eleven members of the Board, nine are appointed by the president and confirmed by the United States Senate (see 39 U.S.C. § 202). The nine appointed members then select the United States postmaster general, who serves as the board's tenth member, and who oversees the day-to-day activities of the service as chief executive officer (see 39 U.S.C. §§ 202–203). The ten-member board then nominates a deputy postmaster general, who acts as chief operating officer, to the eleventh and last remaining open seat.

The independent Postal Regulatory Commission (formerly the Postal Rate Commission) is also controlled by appointees of the president confirmed by the Senate. It oversees postal rates and related concerns, having the authority to approve or reject USPS proposals.

The USPS is often mistaken for a state-owned enterprise or government-owned corporation (e.g., Amtrak) because it operates much like a business. It is, however, an "establishment of the executive branch of the Government of the United States", (39 U.S.C. § 201) as it is controlled by presidential appointees and the postmaster general. As a government agency, it has many special privileges, including sovereign immunity, eminent domain powers, powers to negotiate postal treaties with foreign nations, and an exclusive legal right to deliver first-class and third-class mail. Indeed, in 2004, the U.S. Supreme Court ruled in a unanimous decision “The Postal Service is not subject to antitrust liability. In both form and function, it is not a separate antitrust person from the United States but is part of the Government, and so is not controlled by the antitrust laws.” Sherman Antitrust Act. Unlike a state-owned enterprise, the USPS lacks a transparent ownership structure and isn't subject to standard rules and norms that apply to commercial entities. The USPS also lacks commercial discretion and control.

The U.S. Supreme Court has also upheld the USPS's statutory monopoly on access to letter boxes against a First Amendment freedom of speech challenge; it thus remains illegal in the U.S. for anyone, other than the employees and agents of the USPS, to deliver mailpieces to letter boxes marked "U.S. Mail".

The Postal Service also has a Mailers' Technical Advisory Committee and local Postal Customer Councils, which are advisory and primarily involve business customers.

Privatization proposals

On December 17, 2017, President Donald Trump criticized the postal service's relationship with Amazon. In a post on Twitter, he stated: "Why is the United States Post Office, which is losing many billions of dollars a year, while charging Amazon and others so little to deliver their packages, making Amazon richer and the Post Office dumber and poorer? Should be charging MUCH MORE!" Amazon maintains that the Postal Service makes a profit from its contract with the company.

On June 21, 2018, Trump proposed a sweeping government reorganization that would sharpen the focus on workforce training, consolidate government-assistance programs and shrink federal agencies. As part of this proposal, he recommended restructuring the postal service with an eye toward privatization. According to his proposal, privatization would cut costs and give the financially burdened agency greater flexibility in adjusting to the digital age.

Universal service obligation and monopoly status

Legal basis and rationale

Article I, section 8, Clause 7 of the United States Constitution grants Congress the power to establish post offices and post roads, which has been interpreted as a de facto Congressional monopoly over the delivery of first-class residential mail—which has been defined as non-urgent residential letters (not packages). Accordingly, no other system for delivering first-class residential mail—public or private—has been tolerated, absent Congress's consent.

The mission of the Postal Service is to provide the American public with trusted universal postal service. While not explicitly defined, the Postal Service's universal service obligation (USO) is broadly outlined in statute and includes multiple dimensions: geographic scope, range of products, access to services and facilities, delivery frequency, affordable and uniform pricing, service quality, and security of the mail. While other carriers may claim to voluntarily provide delivery on a broad basis, the Postal Service is the only carrier with a legal obligation to provide all the various aspects of universal service.

Proponents of universal service principles claim that since any obligation must be matched by the financial capability to meet that obligation, the postal monopoly was put in place as a funding mechanism for the USO, and it has been in place for over a hundred years. It consists of two parts: the Private Express Statutes (PES) and the mailbox access rule. The PES refer to the Postal Service's monopoly on the delivery of letters, and the mailbox rule refers to the Postal Service's exclusive access to customer mailboxes.

Proponents of universal service principles further claim that eliminating or reducing the PES or mailbox rule would affect the ability of the Postal Service to provide affordable universal service. If, for example, the PES and the mailbox rule were to be eliminated, and the USO maintained, then either billions of dollars in tax revenues or some other source of funding would have to be found.

Some proponents of universal service principles suggest that private communications that are protected by the veil of government promote the exchange of free ideas and communications. This separates private communications from the ability of a private for-profit or non-profit organization to corrupt. Security for the individual is in this way protected by the United States Post Office, maintaining confidentiality and anonymity, as well as government employees being much less likely to be instructed by superiors to engage in nefarious spying. It is seen by some as a dangerous step to extract the universal service principle from the post office, as the untainted nature of private communications is preserved as assurance of the protection of individual freedom of privacy.

However, as the recent notice of a termination of mail service to residents of the Frank Church—River of No Return Wilderness indicates, mail service has been contracted to private firms such as Arnold Aviation for many decades. KTVB-TV reported:

"We cannot go out every week and pick up our mail ... it's impossible", said Heinz Sippel. "Everyone gets their mail. Why can't we?" said Sue Anderson. Getting mail delivered, once a week, by airplane is not a luxury, it's a necessity for those who live in Idaho's vast wilderness—those along the Salmon and Selway rivers. It's a service that's been provided to them for more than half a century—mostly by Ray Arnold of Arnold Aviation. The decision was reversed; U.S. Postmaster General John Potter indicated that acceptable service to back country customers could not be achieved in any other fashion than continuing an air mail contract with Arnold Aviation to deliver the mail.

2008 report on universal postal service and the postal monopoly

The Postal Act of 2006 required the Postal Regulatory Commission (PRC) to submit a report to the president and Congress on universal postal service and the postal monopoly in December 2008. The report must include any recommended changes. The Postal Service report supports the requirement that the PRC is to consult with and solicit written comments from the Postal Service. In addition, the Government Accountability Office is required to evaluate broader business model issues by 2011.

On October 15, 2008, the Postal Service submitted a report to the PRC on its position related to the Universal Service Obligation (USO). It said no changes to the USO and restriction on mailbox access were necessary at this time, but increased regulatory flexibility was required to ensure affordable universal service in the future. In 2013, the Postal Service announced that starting August 2013, Saturday delivery would be discontinued. 

Obligations of the USO include uniform prices, quality of service, access to services, and six-day delivery to every part of the country. To assure financial support for these obligations, the postal monopoly provides the Postal Service the exclusive right to deliver letters and restricts mailbox access solely for mail. The report argued that eliminating or reducing either aspect of the monopoly "would have a devastating impact on the ability ... to provide the affordable universal service that the country values so highly". Relaxing access to the mailbox would also pose security concerns, increase delivery costs, and hurt customer service, according to the Post Office. The report notes:

It is somewhat misleading to characterize the mailbox rule as a "monopoly," because the enforcement of 18 U.S.C. § 1725 leaves customers with ample alternative means of delivering their messages. Customers can deliver their messages either by paying postage, by placing messages on or under a door or a doormat, by using newspaper or non-postal boxes, by telephoning or emailing, by engaging in person-to-person delivery in public areas, by tacking or taping their notices on a door post, or by placing advertisements in local newspapers. These methods are comparable in efficacy to communication via the mailbox.

Most of these alternatives are not actually free in some communities. For example, in the Chicago metropolitan area and many other major metros one must get a background check from police and pay a daily fee for the right to solicit or post commercial messages on private property.

Regarding the monopoly on delivery of letters, the report notes that the monopoly is not complete, as there is an exception for letters where either the amount paid for private carriage of the letter equals at least six times the current rate for the first ounce of a single-piece First-Class Mail letter (also known as the "base rate" or "base tariff") or the letter weighs at least 12.5 ounces.

 

The Postal Service said that the USO should continue to be broadly defined and there should be no changes to the postal monopoly. Any changes would have far-reaching effects on customers and the trillion dollar mailing industry. "A more rigidly defined USO would ... ultimately harm the American public and businesses," according to the report, which cautions that any potential change must be studied carefully and the effects fully understood.

Competitors

USPS Terminal Annex building in Los Angeles

 

FedEx and United Parcel Service (UPS) directly compete with USPS Express Mail and package delivery services, making nationwide deliveries of urgent letters and packages. Due to the postal monopoly, they are not allowed to deliver non-urgent letters and may not directly ship to U.S. Mail boxes at residential and commercial destinations. However, both companies have transit agreements with the USPS in which an item can be dropped off with either FedEx or UPS who will then provide shipment up to the destination post office serving the intended recipient where it will be transferred for delivery to the U.S. Mail destination, including Post Office Box destinations. These services also deliver packages which are larger and heavier than USPS will accept. DHL Express was the third major competitor until February 2009, when it ceased domestic delivery operations in the United States.

A variety of other transportation companies in the United States move cargo around the country, but either have limited geographic scope for delivery points, or specialize in items too large to be mailed. Many of the thousands of courier companies focus on same-day delivery, for example, by bicycle messenger.

Although USPS and FedEx are direct competitors, USPS contracts with FedEx for air transport of 2–3 Day Priority Mail  and Priority Mail Express (typically delivered overnight).

Alternative transmission methods

The Post Office Department owned and operated the first public telegraph lines in the United States, starting in 1844 from Washington to Baltimore, and eventually extending to New York, Boston, Buffalo, and Philadelphia. In 1847, the telegraph system was privatized, except for a period during World War I, when it was used to accelerate the delivery of letters arriving at night.

Between 1942 and 1945, "V-Mail" (for "Victory Mail") service was available for military mail. Letters were converted into microfilm and reprinted near the destination, to save room on transport vehicles for military cargo.

In 1970, Western Union in co-operation with the Postal Service introduced the "Mailgram", a special type of telegram offered by Western Union intended for bulk mailing to multiple addressees. The sender would contact WU and submit to them the message to be sent and a list of addressees to mail the requested Mailgrams to. The message and address data were then sent electronically over Western Union's terrestrial network normally used for standard telegrams, with WU's Westar 1 satellite used instead starting in 1974 with its launch, for Mailgram transmission to participating Postal Service centers, who would then print and mail the Mailgrams to the requested addressees.

Similar to WU's Mailgrams was Electronic Computer Originated Mail, offered by the Postal Service from 1982 to 1985. Also known as E-COM, it too was used for bulk mailings. Text was transmitted electronically to one of 25 post offices nationwide. The Postal Service would print the mail and put it in special envelopes bearing a blue E-COM logo. Delivery was assured within 2 days.

To improve accuracy and efficiency, the Postal Service introduced the Intelligent Mail program to complement the ZIP code system. This system, which was intended to replace the deprecated POSTNET system, allows bulk mailers to use pre-printed bar codes to assist in mail delivery and sorting. Additional features, called Enhanced, or Full-Service, Intelligent Mail Barcodes allow for mail tracking of bulk mail through the postal system up to the final delivery Post Office.

Criticism of the universal service requirement and the postal monopoly

Critics of the universal service requirement and the statutory postal monopoly include several professional economists advocating for the privatization of the mail delivery system, or at least a relaxation of the universal service model that currently exists. Rick Geddes argued in 2000:

• First, basic economics implies that rural customers are unlikely to be without service under competition; they would simply have to pay the true cost of delivery to them, which may or may not be lower than under monopoly.
• Second, basic notions of fairness imply that the cross-subsidy should be eliminated. To the extent that people make choices about where they live, they should assume the costs of that decision.
• Third, there is no reason why the government monopoly is necessary to ensure service to sparsely populated areas. The government could easily award competitive contracts to private firms for that service.
• Fourth, early concerns that rural residents of the United States would somehow become isolated without federally subsidized mail delivery today are simply unfounded. ... Once both sender and receiver have access to a computer, the marginal cost of sending an electronic message is close to zero.

Furthermore, some economists have argued that because public enterprises may pursue objectives different than profit maximization, they might have more of an incentive than profit-maximizing firms to behave anticompetitively through policies such as predatory pricing, misstating costs, and creating barriers to entry. To resolve those issues, one economist proposes a cost-allocation model that would determine the optimal allocation of USPS's common costs by finding the share of costs that would maximize USPS profits from its competitive products. Postal regulators could use such a cost model to ensure that the Postal Service is not abusing its statutory monopoly by subsidizing price cuts in competitive product markets with revenue obtained from the monopolized market.

Law enforcement agencies

Under the Mail Cover Program USPS photographs the front and back of every piece of U.S. mail as part of the sorting process, enabling law enforcement to obtain address information and images of the outsides of mail as part of an investigation without the need for a warrant.

The Food and Drug Administration inspects packages for illegal drug shipments

Postal Inspection Service

The United States Postal Inspection Service (USPIS) is one of the oldest law enforcement agencies in the U.S. Founded by Benjamin Franklin on August 7, 1775, its mission is to protect the Postal Service, its employees, and its customers from crime and protect the nation's mail system from criminal misuse.

Postal Inspectors enforce over 200 federal laws providing for the protection of mail in investigations of crimes that may adversely affect or fraudulently use the U.S. Mail, the postal system or postal employees.

The USPIS has the power to enforce the USPS monopoly by conducting search and seizure raids on entities they suspect of sending non-urgent mail through overnight delivery competitors. According to the American Enterprise Institute, a private conservative think tank, the USPIS raided Equifax offices in 1993 to ascertain if the mail they were sending through Federal Express was truly "extremely urgent". It was found that the mail was not, and Equifax was fined $30,000.

The PIS oversees the activities of the Postal Police Force who patrol and secure major postal facilities in the United States.

Office of Inspector General

The United States Postal Service Office of Inspector General (OIG) was authorized by law in 1996. Prior to the 1996 legislation, the Postal Inspection Service performed the duties of the OIG. The inspector general, who is independent of postal management, is appointed by and reports directly to the nine presidentially appointed, Senate–confirmed members of the Board of Governors of the United States Postal Service.

The primary purpose of the OIG is to prevent, detect and report fraud, waste and program abuse, and promote efficiency in the operations of the Postal Service. The OIG has "oversight" responsibility for all activities of the Postal Inspection Service.

How delivery services work

Elements of addressing and preparing domestic mail

All mailable articles (e.g., letters, flats, machinable parcels, irregular parcels, etc.) shipped within the United States must comply with an array of standards published in the USPS Domestic Mail Manual (DMM). Before addressing the mailpiece, one must first comply with the various mailability standards relating to attributes of the actual mailpiece such as: minimum/maximum dimensions and weight, acceptable mailing containers, proper mailpiece sealing/closure, utilization of various markings, and restrictions relating to various hazardous (e.g., explosives, flammables, etc.) and restricted (e.g., cigarettes, smokeless tobacco, etc.) materials, as well as others articulated in § 601 of the DMM.

The USPS specifies the following key elements when preparing the face of a mailpiece:

1. Proper Placement: The Delivery Address should be left-justified and located roughly in the center of mailpiece's largest side. More precisely, on a letter-size piece, the recommended address placement is within the optical character reader (OCR) read area, which is a space on the address side of the mailpiece defined by these boundaries: Left – 1/2 inch (13 mm) from the left edge of the piece; Right – 1/2 inch (13 mm) from the right edge of the piece; Top – 2-3/4 inches (70 mm) from the bottom edge of the piece; Bottom – 5/8 inch (16 mm) from the bottom edge of the piece. Preferred placement of a return address is in the upper left portion of the mailpiece—on the side of the piece bearing postage. Finally, postage (e.g., stamps, meter imprints, information-based indicia [IBI], etc.) is to be affixed in the upper right corner of the address side of the mail cover. Any stamp/indicia partly concealed or otherwise obscured by an overlapping stamp/indicia may not be counted as valid postage.
2. Delivery Address (party receiving mail): The mail piece must have the address of the intended recipient, visible and legible, only on the side of the mail piece bearing postage. Generally, the name of the addressee should be included above the address itself. A ZIP+4 code will facilitate delivery.
3. Return Address (party sending mail): A return address tells the USPS where the sender wants the mail returned if it is undeliverable. Usage of a return address is required for some postal services (including Priority Mail, Express Mail, Periodicals in envelopes or wrappers, Insured Mail, Registered Mail, and parcel services).
4. Postage Payment: All mailpieces must include appropriate valid postage. Postage payment may be in the form of stamps, stamped stationery, precanceled stamps, postage meter imprints & PC Postage products ("Postage Evidencing Systems"), or permit imprint (indicia). Members of the U.S. Congress, among others, have franking privileges, which require only a signature.

Domestic First-Class Mail costs 55¢ for envelopes (35¢ for post cards) and upwards, depending on the weight and dimensions of the letter and the class.

Mail going to naval vessels is known as the Fleet Post Office (FPO) and to Army or Air Force installations use the city abbreviation APO (Army Post Office or Air Force Post Office).

Undeliverable mail that cannot be readily returned, including mail without a return address, is treated as dead mail at a Mail Recovery Center in Atlanta, Georgia or Saint Paul, Minnesota.

Sticker promoting ZIP code use

The format of the address is as follows

Line 1: Name of recipient

Line 2: Street address or P.O. Box

Line 3: City, State (ISO 3166-2:US code or APO/FPO code) and ZIP+4 code

Example

Clifford Clavin

84 Beacon Street

Boston MA 02108-3496

The USPS maintains a list of proper abbreviations.

The format of a return address is similar. Though some style manuals recommend using a comma between the city and state name when typesetting addresses in other contexts, for optimal automatic character recognition, the Post Office does not recommend this when addressing mail. The official recommendation is to use all upper case block letters with proper formats and abbreviations, and leave out all punctuation except for the hyphen in the ZIP+4 code. If the address is unusually formatted or illegible enough, it will require hand-processing, delaying that particular item. The USPS publishes the entirety of their postal addressing standards.

Postal address verification tools and services are offered by the USPS and third party companies to help ensure mail is deliverable by fixing formatting, appending information such as ZIP code and validating the address is a valid delivery point. Customers can look up ZIP codes and verify addresses using USPS Web Tools available on the official USPS website and Facebook page, as well as on third-party sites.

Delivery Point Validation

Delivery Point Validation (DPV) provides the highest level of address accuracy checking. In a DPV process, the address is checked against the AMS data file to ensure that it exists as an active delivery point. The USPS does not offer DPV validation on their website; however, there are companies that offer services to perform DPV verification.

Paying postage

The actual postage can be paid via:

• Stamps purchased online at usps.com, at a post office, from a stamp vending machine or "Automated Postal Center" which can also handle packages, or from a third party (such as a grocery store)
• Pre-cancelled stamps for bulk mailings
• Postal meter
• Prepaid envelope
• Shipping label purchased online and printed by the customer on standard paper (e.g. with Click-N-Ship, or via a third-party such as PayPal or Amazon shipping)

All unused U.S. postage stamps issued since 1861 are still valid as postage at their indicated value. Stamps with no value shown or denominated by a letter are also still valid, although the value depends upon the particular stamp. For some stamps issued without a printed value, the current value is the original value. But some stamps beginning in 1988 or earlier, including Forever Stamps (issued from April 2007) and all first-class, first-ounce stamps issued from January 21, 2011, the value is the current value of a first-class-mail first-ounce stamp. The USPS calls these Forever Stamps but the generic name is non-denominated postage.

Forever stamps are sold at the First-Class Mail postage rate at the time of purchase, but will always be valid for First-Class Mail, up to 1 ounce (28 g), no matter how rates rise in the future. Britain has had a similar stamp since 1989. The cost of mailing a 1 oz (28 g) First-Class letter increased to 55 cents on January 26, 2020.

Postage meters

A postage meter is a mechanical device used to create and apply physical evidence of postage (or franking) to mailed matter. Postage meters are regulated by a country's postal authority; for example, in the United States, the United States Postal Service specifies the rules for the creation, support, and use of postage meters. A postage meter imprints an amount of postage, functioning as a postage stamp, a cancellation and a dated postmark all in one. The meter stamp serves as proof of payment and eliminates the need for adhesive stamps.

PC Postage

In addition to using standard stamps, postage can now be printed in the form of an electronic stamp, or e-stamp, from a personal computer using a system called Information Based Indicia. This online PC Postage method relies upon application software on the customer's computer contacting a postal security device at the office of the postal service.

PC Postage providers include:

• Stamps.com (founded 1996, headquartered in El Segundo, CA)
• EasyPost (founded 2012, headquartered in San Francisco, CA)

Other electronic postage payment methods

Electronic Verification System (eVS) is the Postal Service's integrated mail management technology that centralizes payment processing and electronic postage reports. Part of an evolving suite of USPS electronic payment services called PostalOne!, eVS allows mailers shipping large volumes of parcels through the Postal Service a way to circumvent use of hard-copy manifests, postage statements and drop-shipment verification forms. Instead, mailers can pay postage automatically through a centralized account and track payments online.

Beginning in August 2007, the Postal Service began requiring mailers shipping Parcel Select packages using a permit imprint to use eVS for manifesting their packages.

Stamp copyright and reproduction

All U.S. postage stamps issued under the former United States Post Office Department and other postage items that were released before 1978 are not subject to copyright, but stamp designs since 1978 are copyrighted. The United States Copyright Office in section 313.6(C)(1) of the Third Edition of the Compendium of U.S. Copyright Office Practices holds that "Works prepared by officers or employees of the U.S. Postal Service ... are not considered works of the U.S. Government" and are therefore eligible for registration. Thus, the USPS holds copyright to such materials released since 1978 under Title 17 of the United States Code. Written permission is required for use of copyrighted postage stamp images, although under USPS rules, permission is "generally" not required for "educational use", "news reporting" or "philatelic advertising use," but users must cite USPS as the source of the image and include language such as "© United States Postal Service. All rights reserved."

Service level choices

General domestic services

Former Tyvek envelope design for Express Mail before July 28, 2013

As of April 2011, domestic postage levels for low-volume mailers include:

• Priority Mail Express (Formerly Express Mail): Overnight delivery guaranteed to most locations
  • Sunday, holiday and 10:30 am delivery available for additional charge.
  • $100 insurance included.
  • Tracking included.
  • Flat Rate envelopes are available. Otherwise, pricing varies by weight and distance.
• Priority Mail: Day specific delivery service ranging from 1–3 days depending on origin of shipment (not guaranteed)
  • As of January 27, 2013, tracking via Delivery Confirmation is now included on all Priority Mail shipments.
  • Flat Rate envelopes and boxes (various sizes) are available free from the Postal Store. Otherwise, pricing varies by weight, size and distance.
  • $50 insurance for retail/$100 insurance for commercial starting on July 28, 2013.
  • Tracking Included
• First-Class Mail
  • 2- to 3-day delivery.
    • In most cases for letters and small packages.
  • Rate varies by size and weight, but not distance.
    • Postcards (5" × 3.5" × 0.007 to 6" × 4.25" × 0.016" [127 × 89 × 0.18 to 152 × 108 × 0.4 mm]): 35¢
    • Letters (up to 11.5" × 6.125" × 0.25", 3.5 oz [292 × 156 × 6.4 mm, 100 g]): 55¢ + 15¢ for each additional ounce stamped, 50¢ + 15¢ for each additional ounce metered
    • Large Envelope or Flat (up to 15" × 12" × 0.75", 13 oz [381 × 305 × 19 mm, 370 g]): $1.00 + 15¢ each additional ounce (28 g). Must be rectangular, uniformly thick, and not too rigid.
• First class package service
  • Rate varies by weight and distance.
    • Package/Parcel (Up to 108 inches (270 cm) length plus girth, 13 ounces (370 g): $3.80-$4.20 up to 4 ounces, $4.60-$5.00 up to 8 ounces, $5.90-$6.50 up to 13 ounces
• USPS Retail Ground (formerly Parcel Post)
  • Slowest but cheapest service for packages too large or heavy for First Class—uses surface transport.
  • 2- to 9-day service to contiguous U.S., 4–14 days internal to AK/HI/territories, 3–6 weeks between mainland and outlying areas (travels by ship).
  • Variable pricing by weight, size and distance.
  • Free forwarding if recipient has filed change-of-address form, or return if the item is undeliverable.
• Media Mail—formerly "Book Rate"
  • Books and recorded media only.
  • No advertising.
  • Pricing by weight only.
  • Transit time similar to Parcel Post.
  • Cheaper than Parcel Post but only due to increased restrictions on package contents.
• Library Mail
  • Similar to Media Mail, but cheaper and restricted to academic institutions, public libraries, museums, etc.

The Post Office will not deliver packages heavier than 70 pounds (32 kg) or if the length (the package's longest dimension) plus the girth (the measurement around the package at its largest point in the two shorter dimensions) is greater than 108 inches (270 cm) combined (130 inches [330 cm] for Parcel Post)

Bulk mail

USPS Dodge Caravan used for residential delivery in Omaha, Nebraska

 

USPS-operated minivan serving in the LLV's role

 

Discounts are available for large volumes of mail. Depending on the postage level, certain conditions might be required or optional for an additional discount:

• Minimum number of pieces
• Weight limits
• Ability for the USPS to process by machine
• Addresses formatting standardized
• USPS-readable barcode
• Sorted by three-digit ZIP code prefix, five-digit ZIP code, ZIP+4, or 11-digit delivery point
• Delivered in trays, bundles, or pallets partitioned by destination
• Delivered directly to a regional Bulk Mail Center, destination SCF, or destination Post Office
• Certification of mailing list accuracy and freshness (e.g. correct ZIP codes, purging of stale addresses, processing of change-of-address notifications)

In addition to bulk discounts on Express, Priority, and First-Class Mail, the following postage levels are available for bulk mailers:

• Periodicals
• Standard Mail (A)
  • Automation
  • Enhanced Carrier Route
  • Regular
• Standard Mail (B)
  • Parcel Post
  • Bound Printed Matter – Cheaper than Media Mail, for advertising catalogs, phone books, etc. up to 15 lb
  • Special Standard Mail
  • Library Mail
  • Nonprofit

Extra services

A Long Life Vehicle seen in Guam

 

Depending on the type of mail, additional services are available for an additional fee:

• Certificate of Mailing provides proof of the date a package was mailed.
• Certified Mail provides proof of mailing, and a delivery record. Used for serving legal documents and for sending U.S. Government classified information, up to the "confidential" level.
• Collect on Delivery (C.O.D.) allows merchants to offer customers an option to pay upon delivery, up to $1000. Includes insurance.
• USPS Tracking provides proof of delivery to sorting facilities, local post office and destination, but no signature is required.
• Insurance is shipping insurance against loss or damage for the value of the goods mailed. Amount of coverage can be specified, up to $5,000.
• Registered Mail is used for highly valuable or irreplaceable items, and classified information up to the "secret" level.^[148] Registered mail is transported separately from other mail, in locked containers. Tracking is included and insurance up to $25,000 is available.^[149]
• Restricted Delivery requires delivery to a specific person or their authorized agent, not just to a mailbox.
• Return Receipt actively sends signature confirmation back to the sender by postcard or emailed PDF (as opposed to merely putting this information into the online tracking system).
• Signature Confirmation requires a delivery signature, which is kept on file. The online tracking system displays the first initial and last name of the signatory.
• Special Handling is for unusual items, like live animals.

International services

Packages awaiting inspection at the International Mail Facility in JFK airport

In May 2007, the USPS restructured international service names to correspond with domestic shipping options. Formerly, USPS International services were categorized as Airmail (Letter Post), Economy (Surface) Parcel Post, Airmail Parcel Post, Global Priority, Global Express, and Global Express Guaranteed Mail. The former Airmail (Letter Post) is now First-Class Mail International, and includes small packages weighing up to four pounds (1.8 kg). Economy Parcel Post was discontinued for international service, while Airmail Parcel Post was replaced by Priority Mail International. Priority Mail International Flat-Rate packaging in various sizes was introduced, with the same conditions of service previously used for Global Priority. Global Express is now Express Mail International, while Global Express Guaranteed is unchanged. The international mailing classes with a tracking ability are Express, Express Guaranteed, and Priority (except that tracking is not available for Priority Mail International Flat Rate Envelopes or Priority Mail International Small Flat Rate Boxes).

One of the major changes in the new naming and services definitions is that USPS-supplied mailing boxes for Priority and Express mail are now allowed for international use. These services are offered to ship letters and packages to almost every country and territory on the globe. The USPS provides much of this service by contracting with a private parcel service, FedEx.

An m-bag

The USPS provides an M-bag service for international shipment of printed matter; previously surface M-bags existed, but with the 2007 elimination of surface mail, only airmail M-bags remain. The term "M-bag" is not expanded in USPS publications; M-bags are simply defined as "direct sacks of printed matter ... sent to a single foreign addressee at a single address"; however, the term is sometimes referred to informally as "media bag", as the bag can also contain "discs, tapes, and cassettes", in addition to books, for which the usual umbrella term is "media"; some also refer to them as "mail bags".

Military mail is billed at domestic rates when being sent from the United States to a military outpost, and is free when sent by deployed military personnel. The overseas logistics are handled by the Military Postal Service Agency in the Department of Defense. Outside of forward areas and active operations, military mail First-Class takes 7–10 days, Priority 10–15 days, and Parcel Post about 24 days.

Three independent countries with a Compact of Free Association with the U.S. (Palau, the Marshall Islands, and the Federated States of Micronesia) have a special relationship with the United States Postal Service:

• Each associated state maintains its own government-run mail service for delivery to and pickup from retail customers.
• The associated states are integrated into the USPS addressing and ZIP code system.
• The USPS is responsible for transporting mail between the United States and the associated states, and between the individual states of the Federated States of Micronesia.
• The associated states synchronize postal services and rates with the USPS.
• The USPS treats mail to and from the associated states as domestic mail. Incoming mail does require customs declarations because, like some U.S. territories, the associated states are outside the main customs territory of the United States.

The discontinuation of international surface mail

For more information about surface mail, see Surface mail.

 

In 2007, the US Postal Service discontinued its outbound international surface mail ("sea mail") service, mainly because of increased costs. Returned undeliverable surface parcels had become an expensive problem for the USPS, since it was often required to take such parcels back.

Domestic surface mail (now "Retail Ground" or "Commercial Parcel Select") remains available.

Alternatives to international surface mail include:

• International Surface Air Lift (ISAL). The service includes neither tracking nor insurance; but it may be possible to purchase shipping insurance from a third-party company.
• USPS Commercial ePacket. The service is trackable.
• Ordinary first-class international airmail.

Senders can access the International Surface Air Lift and ePacket services through postal wholesalers. Some examples of such wholesalers include:

• Asendia USA (accessible through the Shippo website to users who have an Asendia account),
• Globegistics (now owned by Asendia), and
• APC Postal Logistics.

If a sender sends an ISAL mailing directly through the USPS (without a wholesaler as an intermediary), the minimum weight is 50 pounds per mailing.

Sorting and delivery process

Mail flow through national infrastructure

Processing of standard sized envelopes and cards is highly automated, including reading of handwritten addresses. Mail from individual customers and public postboxes is collected by letter carriers into plastic tubs, which are taken to one of approximately 251 Processing and Distribution Centers (P&DC) across the United States. Each P&DC sorts mail for a given region (typically with a radius of around 200 miles (320 km)) and connects with the national network for interregional mail. The USPS has consolidated mail sorting for large regions into the P&DCs on the basis that most mail is addressed to faraway destinations, but for cities at the edge of a P&DC's region, this means all locally addressed mail must now travel long distances (that is, to and from the P&DC for sorting) to reach nearby addresses.

At the P&DC, mail is emptied into hampers which are then automatically dumped into a Dual Pass Rough Cull System (DPRCS). As mail travels through the DPRCS, large items, such as packages and mail bundles, are removed from the stream. As the remaining mail enters the first machine for processing standard mail, the Advanced Facer-Canceler System (AFCS), pieces that passed through the DPRCS but do not conform to physical dimensions for processing in the AFCS (e.g., large envelopes or overstuffed standard envelopes) are automatically diverted from the stream. Mail removed from the DPRCS and AFCS is manually processed or sent to parcel sorting machines.

In contrast to the previous system, which merely canceled and postmarked the upper right corner of the envelope, thereby missing any stamps which were inappropriately placed, the Advanced Facer-Canceler System locates indicia (stamp or metered postage mark), regardless of the orientation of the mail as it enters the machine, and cancels it by applying a postmark. Detection of indicia enables the AFCS to determine the orientation of each mailpiece and sort it accordingly, rotating pieces as necessary so all mail is sorted right-side up and faced in the same direction in each output bin. 

Mail is output by the machine into three categories: mail already affixed with a bar code and addressed (such as business reply envelopes and cards); mail with machine printed (typed) addresses; and mail with handwritten addresses. Additionally, machines with a recent Optical Character Recognition (OCR) upgrade have the capability to read the address information, including handwritten, and sort the mail based on local or outgoing ZIP codes.

Mail with typed addresses goes to a Multiline Optical Character Reader (MLOCR) which reads the ZIP Code and address information and prints the appropriate bar code onto the envelope. Mail (actually the scanned image of the mail) with handwritten addresses (and machine-printed ones that are not easily recognized) goes to the Remote Bar Coding System. It also corrects spelling errors and, where there is an error, omission, or conflict in the written address, identifies the most likely correct address.

When it has decided on a correct address, it prints the appropriate bar code onto the envelopes, similarly to the MLOCR system. RBCS also has facilities in place, called Remote Encoding Centers, that have humans look at images of mail pieces and enter the address data. The address data is associated with the image via an ID Tag, a fluorescent barcode printed by mail processing equipment on the back of mail pieces. 

Processed mail is imaged by the Mail Isolation Control and Tracking (MICT) system to allow easier tracking of hazardous substances. Images are taken at more than 200 mail processing centers, and are destroyed after being retained for 30 days.

If a customer has filed a change of address card and his or her mail is detected in the mailstream with the old address, the mailpiece is sent to a machine that automatically connects to a Computerized Forwarding System database to determine the new address. If this address is found, the machine will paste a label over the former address with the current address. The mail is returned to the mailstream to forward to the new location. 

Mail with addresses that cannot be resolved by the automated system are separated for human intervention. If a local postal worker can read the address, he or she manually sorts it out according to the ZIP code on the article. If the address cannot be read, mail is either returned to the sender (First-Class Mail with a valid return address) or is sent to the Mail Recovery Center in Atlanta, Georgia (formerly known as the dead letter office). At this office, the mail is opened to try to find an address to forward to. If an address is found, the contents are resealed and delivered. Otherwise, the items are held for 90 days in case of inquiry by the customer; if they are not claimed, they are either destroyed or auctioned off at the monthly Postal Service Unclaimed Parcel auction to raise money for the service. 

Once the mail is bar coded, it is automatically sorted by a Delivery Bar Code Sorter (DBCS) that reads the bar code, identifies the destination of the mailpiece, and sends it to an appropriate tray that corresponds to the next segment of its journey.

Regional mail is either trucked to the appropriate local post office, or kept in the building for carrier routes served directly from the P&DC. Out-of-region mail is trucked to the airport and then flown, usually as baggage on commercial airlines, to the airport nearest the destination station. At the destination P&DC, mail is once again read by a DBCS which sorts items to local post offices; this includes grouping mailpieces by individual letter-carrier route. 

At the carrier route level, 95% of letters arrive pre-sorted; the remaining mail must be sorted by hand. The Post Office is working to increase the percentage of automatically sorted mail, including a pilot program to sort "flats".

FedEx provides air transport service to USPS for Priority and Express Mail. Priority Mail and Express Mail are transported from Priority Mail processing centers to the closest FedEx-served airport, where they are handed off to FedEx. FedEx then flies them to the destination airport and hands them back to USPS for transport to the local post office and delivery.

Types of postal facilities

Historic main post office in Tomah, Wisconsin

 

A typical post office station in the Spring Branch area of Houston, Texas

 

A combined Post Office, Customs House, and Federal Court House in Galveston, Texas

 

Floating post office, Halibut Cove, Alaska

 

Although its customer service centers are called post offices in regular speech, the USPS recognizes several types of postal facilities, including the following:

• A main post office (formerly known as a general post office) is the primary postal facility in a community.
• A station or post office station is a postal facility that is not the main post office, but that is within the corporate limits of the community.
• A branch or post office branch is a postal facility that is not the main post office and that is outside the corporate limits of the community.
• A classified unit is a station or branch operated by USPS employees in a facility owned or leased by the USPS.
• A contract postal unit (or CPU) is a station or branch operated by a contractor, typically in a store or other place of business.
• A community post office (or CPO) is a contract postal unit providing services in a small community in which other types of post office facilities have been discontinued.
• A finance unit is a station or branch that provides window services and accepts mail, but does not provide delivery.
• A village post office (VPO) is an entity such as a local business or government center that provides postal services through a contract with the USPS. First introduced in 2011 as an integral part of the USPS plan to close low volume post offices, village post offices will fill the role of the post office within a ZIP code.
• A processing and distribution center (P&DC, or processing and distribution facility, formerly known as a General Mail Facility) is a central mail facility that processes and dispatches incoming and outgoing mail to and from a designated service area (251 nationwide).
• A sectional center facility (SCF) is a P&DC for a designated geographical area defined by one or more three-digit ZIP code prefixes.
• An international service center (ISC) is an international mail processing facility. There are only five such USPS facilities in the continental United States, located in Chicago, New York, Miami, Los Angeles and San Francisco.
• A network distribution center, formerly known as a bulk mail center (BMC), is a central mail facility that processes bulk rate parcels as the hub in a hub and spoke network.
• An auxiliary sorting facility (ASF) is a central mail facility that processes bulk rate parcels as spokes in a hub and spoke network.
• A remote encoding center (REC) is a facility at which clerks receive images of problem mail pieces (those with hard-to-read addresses, etc.) via secure Internet-type feeds and manually type the addresses they can decipher, using a special encoding protocol. The mail pieces are then sprayed with the correct addresses or are sorted for further handling according to the instructions given via encoding. The total number of RECs is down from 55 in 1998 to just 1 center in December 2016. The last REC is in Salt Lake City, Utah.

While common usage refers to all types of postal facilities as "substations", the USPS Glossary of Postal Terms does not define or even list that word. Post Offices often share facilities with other governmental organizations located within a city's central business district. In those locations, often Courthouses and Federal Buildings, the building is owned by the General Services Administration while the U.S. Postal Services operates as a tenant. The USPS retail system has approximately 36,000 post offices, stations, and branches.

Automated Postal Centers

A 24-hour Automated Postal Center kiosk inside the Webster, Texas main post office

 

In the year 2004, the USPS began deploying Automated Postal Centers (APCs). APCs are unattended kiosks that are capable of weighing, franking, and storing packages for later pickup as well as selling domestic and international postage stamps. Since its introduction, APCs do not take cash payments – they only accept credit or debit cards. Similarly, traditional vending machines are available at many post offices to purchase stamps, though these are being phased out in many areas. Due to increasing use of Internet services, as of June 2009, no retail post office windows are open 24 hours; overnight services are limited to those provided by an Automated Postal Center.

Evolutionary Network Development (END) program

In February 2006, the USPS announced that they plan to replace the nine existing facility-types with five processing facility-types:

• Regional Distribution Centers (RDCs), which will process all classes of parcels and bundles and serve as Surface Transfer Centers;
• Local Processing Centers (LPCs), which will process single-piece letters and flats and cancel mail;
• Destination Processing Centers (DPC), sort the mail for individual letter-carrier route;
• Airport Transfer Centers (ATCs), which will serve as transfer points only; and
• Remote Encoding Centers (RECs).

Over a period of years, these facilities are expected to replace Processing & Distribution Centers, Customer Service Facilities, Bulk Mail Centers, Logistic and Distribution Centers, annexes, the Hub and Spoke Program, Air Mail Centers, and International Service Centers.

The changes are a result of the declining volumes of single-piece First-Class Mail, population shifts, the increase in drop shipments by advertising mailers at destinating postal facilities, advancements in equipment and technology, redundancies in the existing network, and the need for operational flexibility.

The program was ended in early 2007 after an analysis revealed that the significant amount of capital investment required to implement the END network concept would not generate the benefits originally anticipated.

Airline and rail division

A former United States Postal Service Boeing 727-200 aircraft at Miami International Airport in 1999

The United States Postal Service does not directly own or operate any aircraft or trains, although both were formerly operated. The mail and packages are flown on airlines with which the Postal Service has a contractual agreement. The contracts change periodically. Contract airlines have included: UPS, Emery Worldwide, Ryan International Airlines, FedEx Express, American Airlines, United Airlines, and Express One International. Amtrak carried some mail between cities, such as Chicago and Minneapolis–Saint Paul, but this terminated in October 2004.

The last air delivery route in the continental U.S., to residents in the Frank Church–River of No Return Wilderness, was scheduled to be ended in June 2009. The weekly bush plane route, contracted out to an air taxi company, had in its final year an annual cost of $46,000, or $2400/year per residence, over ten times the average cost of delivering mail to a residence in the United States. This decision has been reversed by the U.S. postmaster general.

Parcel forwarding and private interchange

Private US parcel forwarding or US mail forwarding companies focusing on personal shopper, relocation, Ex-pat and mail box services often interface with the United States Postal Service for transporting of mail and packages for their customers.

Delivery timing

USPS contractor-driven semi-trailer truck seen near Mendota, California

 

1998 United States Postal Service Ford Windstar, showing the larger driver's side door

Delivery days

From 1810, mail was delivered seven days a week. In 1828, local religious leaders noticed a decline in Sunday-morning church attendance because of local post offices' doubling as gathering places. These leaders appealed to the government to intervene and close post offices on Sundays. The government, however, declined, and mail was delivered 7 days a week until 1912.

Today, U.S. Mail (with the exception of Express Mail) is not delivered on Sunday. 

Saturday delivery was temporarily suspended in April 1957, because of lack of funds, but quickly restored.

Budget problems prompted consideration of dropping Saturday delivery starting around 2009. This culminated in a 2013 announcement that regular mail services would be cut to five days a week, which was reversed by Congress before it could take effect. (See the section Revenue decline and planned cuts.)

Direct delivery vs. customer pickup

Originally, mail was not delivered to homes and businesses, but to post offices. In 1863, "city delivery" began in urban areas with enough customers to make this economical. This required streets to be named, houses to be numbered, with sidewalks and lighting provided, and these street addresses to be added to envelopes. The number of routes served expanded over time. In 1891, the first experiments with Rural Free Delivery began in less densely populated areas. There is currently an effort to reduce direct delivery in favor of mailbox clusters.

To compensate for high mail volume and slow long-distance transportation which saw mail arrive at post offices throughout the day, deliveries were made multiple times a day. This ranged from twice for residential areas to up to seven times for the central business district of Brooklyn, New York. In the late 19th century, mail boxes were encouraged, saving carriers the time it took to deliver directly to the addressee in person; in the 1910s and 1920s, they were phased in as a requirement for service. In the 1940s, multiple daily deliveries began to be reduced, especially on Saturdays. By 1990, the last twice-daily deliveries in New York City were eliminated.

Today, mail is delivered once a day on-site to most private homes and businesses. The USPS still distinguishes between city delivery (where carriers generally walk and deliver to mailboxes hung on exterior walls or porches, or to commercial reception areas) and rural delivery (where carriers generally drive). With "curbside delivery", mailboxes are at the ends of driveways, on the nearest convenient road. "Central point delivery" is used in some locations, where several nearby residences share a "cluster" of individual mailboxes in a single housing. 

Some customers choose to use post office boxes for an additional fee, for privacy or convenience. This provides a locked box at the post office to which mail is addressed and delivered (usually earlier in the day than home delivery). Customers in less densely populated areas where there is no city delivery and who do not qualify for rural delivery may receive mail only through post office boxes. High-volume business customers can also arrange for special pick-up.  Another option is the old-style general delivery, for people who have neither post office boxes nor street addresses. Mail is held at the post office until they present identification and pick it up. 

Some customers receive free post office boxes if the USPS declines to provide door-to-door delivery to their location or a nearby box. People with medical problems can request door-to-door delivery. Homeless people are also eligible for post office boxes at the discretion of the local postmaster, or can use general delivery.

Special delivery

From 1885 to 1997, a service called special delivery was available, which caused a separate delivery to the final location earlier in the day than the usual daily rounds.

Same-day trials

In December 2012, the USPS began a limited one-year trial of same-day deliveries directly from retailers or distribution hubs to residential addresses in the same local area, a service it dubbed "Metro Post". The trial was initially limited to San Francisco and the only retailer to participate in the first few weeks was 1-800-FLOWERS.

In March 2013, the USPS faced new same-day competition for e-commerce deliveries from Google Shopping Express. 

In November 2013, the Postal Service began regular package delivery on Sundays for Amazon customers in New York and Los Angeles, which it expanded to 15 cities in May 2014. Amazon Sunday delivery has now been expanded to most major markets as of September 2015.

Other competition in this area includes online grocers such as AmazonFresh, Webvan, and delivery services operated by grocery stores like Peapod and Safeway.

Forwarding and holds

Residential customers can fill out a form to forward mail to a new address, and can also send pre-printed forms to any of their frequent correspondents. They can also put their mail on "hold", for example, while on vacation. The Post Office will store mail during the hold, instead of letting it overflow in the mailbox. These services are not available to large buildings and customers of a commercial mail receiving agency, where mail is subsorted by non-Post Office employees into individual mailboxes.

Financial services

Postal money orders provide a safe alternative to sending cash through the mail, and are available in any amount up to $1,000. Like a bank cheque, money orders are cashable only by the recipient. Unlike a personal bank check, they are prepaid and therefore cannot be returned because of insufficient funds. Money orders are a declining business for the USPS, as companies like PayPal, Venmo and others are offering electronic replacements.

From 1911 to 1967, the Postal Service also operated the United States Postal Savings System, not unlike a savings and loan association with the amount of the deposit limited.

A January 2014 report by the inspector general of the USPS suggested that the agency could earn $8.9 billion per year in revenue by providing financial services, especially in areas where there are no local banks but there is a local post office, and to customers who currently do not have bank accounts.

Employment

A Rural Letter Carrier from Fort Myers, Florida

The Postal Service is the nation's second-largest civilian employer. As of 2019, it employed 633,108 personnel, divided into offices, processing centers, and actual post offices. The United States Postal Service would rank 44th on the 2019 Fortune 500 list, if considered a private company and ranks 136 on Global Fortune 500 list.

Labor unions representing USPS employees include: The American Postal Workers Union (APWU), which represents postal clerks and maintenance, motor vehicle, mail equipment shops, material distribution centers, and operating services and facilities services employees, postal nurses, and IT and accounting; the National Association of Letter Carriers (NALC), which represents city letter carriers; the National Rural Letter Carriers' Association (NRLCA), which represents rural letter carriers; and the National Postal Mail Handlers Union (NPMHU).

USPS employees are divided into major crafts according to the work they engage in:

• letter carriers, also referred to as mailmen or mail carriers, prepare and deliver mail and parcels. They are divided into two categories: City Letter Carriers, who are represented by the NALC, and Rural Letter Carriers, who are represented by the NRLCA. City Carriers are paid hourly with automatic overtime paid after 8 hours or 40 hours a week of duty. City Carriers are required to work in any kind of weather, daylight or dark and carry three bundles of mail (letters in one hand with magazines and other larger mail pieces) on the forearm carrying the mail. Advertisement mail, Every door direct (EDD) and smaller parcels all go in the carriers satchel). Larger parcels, up to a total of 70 lbs. may be delivered at various times of the day or with the mail. Mail routes are outfitted with a number of scanpoints (mailbox barcodes) on random streets every 30 to 40 minutes apart to keep track of the carriers whereabouts in real-time.
• Rural carriers are under a form of salary called "evaluated hours", usually with overtime built into their pay. The evaluated hours are created by having all mail counted for a period of two or four weeks, and a formula used to create the set dollar amount they will be paid for each day worked until the next time the route is counted.
• Mail handlers and processors, prepare, separate, load and unload mail and parcels, by delivery ZIP code and station, for the clerks. They work almost exclusively at the plants or larger mail facilities now after having their duties excessed and reassigned to clerks in Post Offices and Station branches.
• Clerks, have a dual function by design of where their assignment is. Window clerks directly handle customer service needs at the counter, sort box mail and also sort first-class letters, standard and bulk-rate mail for the carriers on the work floor. Clerks may also work alongside mail handlers in large sorting facilities, outside of the public view, sorting mail. Data Conversion Operators, who encode address information at Remote Encoding Centers, are also members of the clerk craft. Mail handlers and Clerks are represented by the NPMHU and the APWU, respectively.

Other non-managerial positions in the USPS include:

• Maintenance and custodians, who see to the overall operation and cleaning of mail sorting machines, work areas, public parking and general facility operations.
• City Carrier Assistants. (CCAs) With the Das Arbitration award the designation of PTF City Carrier has been abolished. TE City Carriers will have the opportunity to become CCAs. A CCA is a non-career employee who is hired for a 360-day term, similar to what TEs had. CCAs earn annual leave. CCAs, unlike TEs do have a direct path to becoming career employees. When excess City Carrier positions exist the CCA in that work installation with the highest "relative standing" will be promoted to a career employee and be assigned to the vacant position.
• Career, Part Time Flexible and Transitional employees (Career, PTF & TE) There are a variety of other non-managerial positions in such crafts as accounting, information technology, and the remote encoding center. These are under a different contract than plant workers or letter carriers.
• Contractors are not USPS employees, but work for the USPS under a written contract and usually paid per mile. They do not get benefits including health insurance, leave, life insurance, and pension. They must use their own vehicle and pay any cost to maintain, insure, or replace. Contractors generally make less than employees. Just like regular carriers they deliver packages and letters to mailboxes and doors.

Though the USPS employs many individuals, as more Americans send information via email, fewer postal workers are needed to work dwindling amounts of mail. Post offices and mail facilities are constantly downsizing, replacing craft positions with new machines and consolidating mail routes through the MIARAP (Modified Interim Alternate Route Adjustment Process) agreement. A major round of job cuts, early retirements, and a construction freeze were announced on March 20, 2009.

Workplace violence

In the early 1990s, widely publicized workplace shootings by disgruntled employees at USPS facilities led to a Human Resource effort to provide care for stressed workers and resources for coworker conflicts. Due to media coverage, postal employees gained a reputation among the general public as more likely to be mentally ill. The USPS Commission on a Safe and Secure Workplace found that "Postal workers are only a third as likely as those in the national workforce to be victims of homicide at work." In the documentary Murder by Proxy: How America Went Postal, it was argued that this number failed to factor out workers killed by external subjects rather than by fellow employees.

This series of events in turn has influenced American culture, as seen in the slang term "going postal" and the computer game Postal. Also, in the opening sequence of Naked Gun ​33 ¹⁄₃: The Final Insult, a yell of "Disgruntled postal workers" is heard, followed by the arrival of postal workers with machine guns. In an episode of Seinfeld, the mailman character, Newman, explained in a dramatic monologue that postal workers "go crazy and kill everyone" because the mail never stops. In The Simpsons episode "Sunday, Cruddy Sunday," Nelson Muntz asks Postmaster Bill if he has "ever gone on a killing spree"; Bill replies, "The day of the gun-toting, disgruntled postman shooting up the place went out with the Macarena".

The series of massacres led the USPS to issue a rule prohibiting the possession of any type of firearms (except for those issued to Postal Inspectors) in all designated USPS facilities.

In 2016, video footage was released showing a group of police officers from the New York City Police Department (NYPD) arresting a USPS worker while he was in the middle of his deliveries. The footage showed that the officers were dressed in civilian clothing. The NYPD is reportedly investigating alleged disorderly conduct.

In fiction

• In the film Miracle on 34th Street (1947), the identity of Kris Kringle (played by Edmund Gwenn) as the one and only "Santa Claus" was validated by a state court, based on the delivery of 21 bags of mail (famously carried into the courtroom) to the character in question. The contention was that it would have been illegal for the United States Post Office to deliver mail that was addressed to "Santa Claus" to the character "Kris Kringle" unless he were, in fact, the one and only Santa Claus. Judge Henry X. Harper (played by Gene Lockhart) ruled that since the U.S. Government had demonstrated through the delivery of the bags of mail that Kris Kringle was Santa Claus, the State of New York did not have the authority to overrule that decision.
• The novel Post Office (1971), written by poet and novelist Charles Bukowski, is a semi-autobiographical account of his life over the years as a letter carrier. Bukowski would, under duress, quit and years later return as a mail clerk. His personal account would detail the work at lengths as frustrating, menial, boring, and degrading.
• David Brin's novel The Postman (1985) portrays the USPS and its returned services as a staple to revive the United States government in a post-apocalyptic world. It was adapted as a film starring Kevin Costner and Larenz Tate in 1997.
• The comedy film Dear God (1996), starring Greg Kinnear and Laurie Metcalf, portrays a group of quirky postal workers in a dead letter office that handle letters addressed to the Easter Bunny, Elvis, and even God himself.
• In 2015, The Inspectors, which depicts a group of postal inspectors investigating postal crimes, debuted on CBS. The series uses the USPIS seal and features messages and tips from the Chief Postal Inspector at the end of each episode.
• Signed, Sealed, Delivered (original title: Dead Letters), also known as Lost Letter Mysteries, is an American-Canadian drama/romantic comedy television series that aired on the Hallmark Channel from April 20 through June 22, 2014.
• In the NBC sitcom Cheers, Cliff Clavin (played by John Ratzenberger) was a know-it-all bar regular and letter carrier.

Human mitochondrial genetics

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Human_mitochondrial_genetics 

 

Human mitochondrial DNA
The 16,569 bp long human mitochondrial genome with the protein-coding, ribosomal RNA, and transfer RNA genes.
Features
Length (bp)	16,569
No. of genes	13 (coding genes) 24 (non coding genes)
Type	Mitochondrial DNA
Complete gene lists
HGNC	Gene list
NCBI	Gene list
External map viewers
Ensembl	Chromosome MT
Entrez	Chromosome MT
NCBI	Chromosome MT
UCSC	Chromosome M
Full DNA sequences
RefSeq	NC_012920 (FASTA)
GenBank	J01415 (FASTA)

Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA (the DNA contained in human mitochondria). The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. Mitochondria are small structures in cells that generate energy for the cell to use, and are hence referred to as the "powerhouses" of the cell.

Mitochondrial DNA (mtDNA) is not transmitted through nuclear DNA (nDNA). In humans, as in most multicellular organisms, mitochondrial DNA is inherited only from the mother's ovum. There are theories, however, that paternal mtDNA transmission in humans can occur under certain circumstances.

Mitochondrial inheritance is therefore non-Mendelian, as Mendelian inheritance presumes that half the genetic material of a fertilized egg (zygote) derives from each parent.

Eighty percent of mitochondrial DNA codes for mitochondrial RNA, and therefore most mitochondrial DNA mutations lead to functional problems, which may be manifested as muscle disorders (myopathies).

Because they provide 30 molecules of ATP per glucose molecule in contrast to the 2 ATP molecules produced by glycolysis, mitochondria are essential to all higher organisms for sustaining life. The mitochondrial diseases are genetic disorders carried in mitochondrial DNA, or nuclear DNA coding for mitochondrial components. Slight problems with any one of the numerous enzymes used by the mitochondria can be devastating to the cell, and in turn, to the organism.

Quantity

In humans, mitochondrial DNA (mtDNA) forms closed circular molecules that contain 16,569 DNA base pairs, with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules, with the quantity ranging between 1 and 15. Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500.

Inheritance patterns

Mitochondrial inheritance patterns

 

The reason for maternal inheritance in mitochondrial DNA is that when the sperm enters the egg cell, it discards its middle part, which contains its mitochondria, so that only its head with the nucleus penetrates the egg cell.

Because mitochondrial diseases (diseases due to malfunction of mitochondria) can be inherited both maternally and through chromosomal inheritance, the way in which they are passed on from generation to generation can vary greatly depending on the disease. Mitochondrial genetic mutations that occur in the nuclear DNA can occur in any of the chromosomes (depending on the species). Mutations inherited through the chromosomes can be autosomal dominant or recessive and can also be sex-linked dominant or recessive. Chromosomal inheritance follows normal Mendelian laws, despite the fact that the phenotype of the disease may be masked.

Because of the complex ways in which mitochondrial and nuclear DNA "communicate" and interact, even seemingly simple inheritance is hard to diagnose. A mutation in chromosomal DNA may change a protein that regulates (increases or decreases) the production of another certain protein in the mitochondria or the cytoplasm; this may lead to slight, if any, noticeable symptoms. On the other hand, some devastating mtDNA mutations are easy to diagnose because of their widespread damage to muscular, neural, and/or hepatic tissues (among other high-energy and metabolism-dependent tissues) and because they are present in the mother and all the offspring. 

The number of affected mtDNA molecules inherited by a specific offspring can vary greatly because

• the mitochondria within the fertilized oocyte is what the new life will have to begin with (in terms of mtDNA),
• the number of affected mitochondria varies from cell (in this case, the fertilized oocyte) to cell depending both on the number it inherited from its mother cell and environmental factors which may favor mutant or wildtype mitochondrial DNA,
• the number of mtDNA molecules in the mitochondria varies from around two to ten.

It is possible, even in twin births, for one baby to receive more than half mutant mtDNA molecules while the other twin may receive only a tiny fraction of mutant mtDNA molecules with respect to wildtype (depending on how the twins divide from each other and how many mutant mitochondria happen to be on each side of the division). In a few cases, some mitochondria or a mitochondrion from the sperm cell enters the oocyte but paternal mitochondria are actively decomposed.

Genes

Electron transport chain, and humanin

It was originally incorrectly believed that the mitochondrial genome contained only 13 protein-coding genes, all of them encoding proteins of the electron transport chain. However, in 2001, a 14th biologically active protein called humanin was discovered, and was found to be encoded by the mitochondrial gene MT-RNR2 which also encodes part of the mitochondrial ribosome (made out of RNA):

Complex number	Category	Genes	Positions in the mitogenome	Strand
I	NADH dehydrogenase
		MT-ND1	3,307–4,262	L
		MT-ND2	4,470–5,511	L
		MT-ND3	10,059–10,404	L
		MT-ND4L	10,470–10,766	L
		MT-ND4	10,760–12,137 (overlap with MT-ND4L)	L
		MT-ND5	12,337–14,148	L
		MT-ND6	14,149–14,673	H
III	Coenzyme Q - cytochrome c reductase / Cytochrome b	MT-CYB	14,747–15,887	L
IV	Cytochrome c oxidase	MT-CO1	5,904–7,445	L
		MT-CO2	7,586–8,269	L
		MT-CO3	9,207–9,990	L
V	ATP synthase	MT-ATP6	8,527–9,207 (overlap with MT-ATP8)	L
		MT-ATP8	8,366–8,572	L
—	Humanin	MT-RNR2	—	—

Unlike the other proteins, humanin does not remain in the mitochondria, and interacts with the rest of the cell and cellular receptors. Humanin can protect brain cells by inhibiting apoptosis. Despite its name, versions of humanin also exist in other animals, such as rattin in rats.

rRNA

The following genes encode rRNAs: 

Subunit	rRNA	Genes	Positions in the mitogenome	Strand
Small (SSU)	12S	MT-RNR1	648–1,601	L
Large (LSU)	16S	MT-RNR2	1,671–3,229	L

tRNA

The following genes encode tRNAs:

Amino Acid	3-Letter	1-Letter	MT DNA	Positions	Strand
Alanine	Ala	A	MT-TA	5,587–5,655	H
Arginine	Arg	R	MT-TR	10,405–10,469	L
Asparagine	Asn	N	MT-TN	5,657–5,729	H
Aspartic acid	Asp	D	MT-TD	7,518–7,585	L
Cysteine	Cys	C	MT-TC	5,761–5,826	H
Glutamic acid	Glu	E	MT-TE	14,674–14,742	H
Glutamine	Gln	Q	MT-TQ	4,329–4,400	H
Glycine	Gly	G	MT-TG	9,991–10,058	L
Histidine	His	H	MT-TH	12,138–12,206	L
Isoleucine	Ile	I	MT-TI	4,263–4,331	L
Leucine	Leu (UUR)	L	MT-TL1	3,230–3,304	L
Leucine	Leu (CUN)	L	MT-TL2	12,266–12,336	L
Lysine	Lys	K	MT-TK	8,295–8,364	L
Methionine	Met	M	MT-TM	4,402–4,469	L
Phenylalanine	Phe	F	MT-TF	577–647	L
Proline	Pro	P	MT-TP	15,956–16,023	H
Serine	Ser (UCN)	S	MT-TS1	7,446–7,514	H
Serine	Ser (AGY)	S	MT-TS2	12,207–12,265	L
Threonine	Thr	T	MT-TT	15,888–15,953	L
Tryptophan	Trp	W	MT-TW	5,512–5,579	L
Tyrosine	Tyr	Y	MT-TY	5,826–5,891	H
Valine	Val	V	MT-TV	1,602–1,670	L

Location of genes

Mitochondrial DNA traditionally had the two strands of DNA designated the heavy and the light strand, due to their buoyant densities during separation in cesium chloride gradients, which was found to be related to the relative G+T nucleotide content of the strand. However, confusion of labeling of this strands is widespread, and appears to originate with an identification of the majority coding strand as the heavy in one influential article in 1999. In humans, the light strand of mtDNA carries 28 genes and the heavy strand of mtDNA carries only 9 genes. Eight of the 9 genes on the heavy strand code for mitochondrial tRNA molecules. Human mtDNA consists of 16,569 nucleotide pairs. The entire molecule is regulated by only one regulatory region which contains the origins of replication of both heavy and light strands. The entire human mitochondrial DNA molecule has been mapped.

Genetic code variants

The genetic code is, for the most part, universal, with few exceptions: mitochondrial genetics includes some of these. For most organisms the "stop codons" are "UAA", "UAG", and "UGA". In vertebrate mitochondria "AGA" and "AGG" are also stop codons, but not "UGA", which codes for tryptophan instead. "AUA" codes for isoleucine in most organisms but for methionine in vertebrate mitochondrial mRNA.

There are many other variations among the codes used by other mitochondrial m/tRNA, which happened not to be harmful to their organisms, and which can be used as a tool (along with other mutations among the mtDNA/RNA of different species) to determine relative proximity of common ancestry of related species. (The more related two species are, the more mtDNA/RNA mutations will be the same in their mitochondrial genome).

Using these techniques, it is estimated that the first mitochondria arose around 1.5 billion years ago. A generally accepted hypothesis is that mitochondria originated as an aerobic prokaryote in a symbiotic relationship within an anaerobic eukaryote.

Replication, repair, transcription, and translation

Mitochondrial replication is controlled by nuclear genes and is specifically suited to make as many mitochondria as that particular cell needs at the time.

Mitochondrial transcription in humans is initiated from three promoters, H1, H2, and L (heavy strand 1, heavy strand 2, and light strand promoters). The H2 promoter transcribes almost the entire heavy strand and the L promoter transcribes the entire light strand. The H1 promoter causes the transcription of the two mitochondrial rRNA molecules.

When transcription takes place on the heavy strand a polycistronic transcript is created. The light strand produces either small transcripts, which can be used as primers, or one long transcript. The production of primers occurs by processing of light strand transcripts with the Mitochondrial RNase MRP (Mitochondrial RNA Processing). The requirement of transcription to produce primers links the process of transcription to mtDNA replication. Full length transcripts are cut into functional tRNA, rRNA, and mRNA molecules.

The process of transcription initiation in mitochondria involves three types of proteins: the mitochondrial RNA polymerase (POLRMT), mitochondrial transcription factor A (TFAM), and mitochondrial transcription factors B1 and B2 (TFB1M, TFB2M). POLRMT, TFAM, and TFB1M or TFB2M assemble at the mitochondrial promoters and begin transcription. The actual molecular events that are involved in initiation are unknown, but these factors make up the basal transcription machinery and have been shown to function in vitro. Mitochondrial translation is still not very well understood. In vitro translations have still not been successful, probably due to the difficulty of isolating sufficient mt mRNA, functional mt rRNA, and possibly because of the complicated changes that the mRNA undergoes before it is translated.

Mitochondrial DNA polymerase

The Mitochondrial DNA Polymerase (Pol gamma, encoded by the POLG gene) is used in the copying of mtDNA during replication. Because the two (heavy and light) strands on the circular mtDNA molecule have different origins of replication, it replicates in a D-loop mode. One strand begins to replicate first, displacing the other strand. This continues until replication reaches the origin of replication on the other strand, at which point the other strand begins replicating in the opposite direction. This results in two new mtDNA molecules. Each mitochondrion has several copies of the mtDNA molecule and the number of mtDNA molecules is a limiting factor in mitochondrial fission. After the mitochondrion has enough mtDNA, membrane area, and membrane proteins, it can undergo fission (very similar to that which bacteria use) to become two mitochondria. Evidence suggests that mitochondria can also undergo fusion and exchange (in a form of crossover) genetic material among each other. Mitochondria sometimes form large matrices in which fusion, fission, and protein exchanges are constantly occurring. mtDNA shared among mitochondria (despite the fact that they can undergo fusion).

Damage and transcription error

Mitochondrial DNA is susceptible to damage from free oxygen radicals from mistakes that occur during the production of ATP through the electron transport chain. These mistakes can be caused by genetic disorders, cancer, and temperature variations. These radicals can damage mtDNA molecules or change them, making it hard for mitochondrial polymerase to replicate them. Both cases can lead to deletions, rearrangements, and other mutations. Recent evidence has suggested that mitochondria have enzymes that proofread mtDNA and fix mutations that may occur due to free radicals. It is believed that a DNA recombinase found in mammalian cells is also involved in a repairing recombination process. Deletions and mutations due to free radicals have been associated with the aging process. It is believed that radicals cause mutations which lead to mutant proteins, which in turn led to more radicals. This process takes many years and is associated with some aging processes involved in oxygen-dependent tissues such as brain, heart, muscle, and kidney. Auto-enhancing processes such as these are possible causes of degenerative diseases including Parkinson's, Alzheimer's, and coronary artery disease.

Chromosomally mediated mtDNA replication errors

Because mitochondrial growth and fission are mediated by the nuclear DNA, mutations in nuclear DNA can have a wide array of effects on mtDNA replication. Despite the fact that the loci for some of these mutations have been found on human chromosomes, specific genes and proteins involved have not yet been isolated. Mitochondria need a certain protein to undergo fission. If this protein (generated by the nucleus) is not present, the mitochondria grow but they do not divide. This leads to giant, inefficient mitochondria. Mistakes in chromosomal genes or their products can also affect mitochondrial replication more directly by inhibiting mitochondrial polymerase and can even cause mutations in the mtDNA directly and indirectly. Indirect mutations are most often caused by radicals created by defective proteins made from nuclear DNA.

Mitochondrial diseases

Contribution of mitochondrial versus nuclear genome

In total, the mitochondrion hosts about 3000 different types of proteins, but only about 13 of them are coded on the mitochondrial DNA. Most of the 3000 types of proteins are involved in a variety of processes other than ATP production, such as porphyrin synthesis. Only about 3% of them code for ATP production proteins. This means most of the genetic information coding for the protein makeup of mitochondria is in chromosomal DNA and is involved in processes other than ATP synthesis. This increases the chances that a mutation that will affect a mitochondrion will occur in chromosomal DNA, which is inherited in a Mendelian pattern. Another result is that a chromosomal mutation will affect a specific tissue due to its specific needs, whether those may be high energy requirements or a need for the catabolism or anabolism of a specific neurotransmitter or nucleic acid. Because several copies of the mitochondrial genome are carried by each mitochondrion (2–10 in humans), mitochondrial mutations can be inherited maternally by mtDNA mutations which are present in mitochondria inside the oocyte before fertilization, or (as stated above) through mutations in the chromosomes.

Presentation

Mitochondrial diseases range in severity from asymptomatic to fatal, and are most commonly due to inherited rather than acquired mutations of mitochondrial DNA. A given mitochondrial mutation can cause various diseases depending on the severity of the problem in the mitochondria and the tissue the affected mitochondria are in. Conversely, several different mutations may present themselves as the same disease. This almost patient-specific characterization of mitochondrial diseases (see Personalized medicine) makes them very hard to accurately recognize, diagnose and trace. Some diseases are observable at or even before birth (many causing death) while others do not show themselves until late adulthood (late-onset disorders). This is because the number of mutant versus wildtype mitochondria varies between cells and tissues, and is continuously changing. Because cells have multiple mitochondria, different mitochondria in the same cell can have different variations of the mtDNA. This condition is referred to as heteroplasmy. When a certain tissue reaches a certain ratio of mutant versus wildtype mitochondria, a disease will present itself. The ratio varies from person to person and tissue to tissue (depending on its specific energy, oxygen, and metabolism requirements, and the effects of the specific mutation). Mitochondrial diseases are very numerous and different. Apart from diseases caused by abnormalities in mitochondrial DNA, many diseases are suspected to be associated in part by mitochondrial dysfunctions, such as diabetes mellitus, forms of cancer and cardiovascular disease, lactic acidosis, specific forms of myopathy, osteoporosis, Alzheimer's disease, Parkinsons's disease, stroke, male infertility and which are also believed to play a role in the aging process.

Use in forensics

Human mtDNA can also be used to help identify individuals. Forensic laboratories occasionally use mtDNA comparison to identify human remains, and especially to identify older unidentified skeletal remains. Although unlike nuclear DNA, mtDNA is not specific to one individual, it can be used in combination with other evidence (anthropological evidence, circumstantial evidence, and the like) to establish identification. mtDNA is also used to exclude possible matches between missing persons and unidentified remains. Many researchers believe that mtDNA is better suited to identification of older skeletal remains than nuclear DNA because the greater number of copies of mtDNA per cell increases the chance of obtaining a useful sample, and because a match with a living relative is possible even if numerous maternal generations separate the two.

Examples

American outlaw Jesse James's remains were identified using a comparison between mtDNA extracted from his remains and the mtDNA of the son of the female-line great-granddaughter of his sister.

Similarly, the remains of Alexandra Feodorovna (Alix of Hesse), last Empress of Russia, and her children were identified by comparison of their mitochondrial DNA with that of Prince Philip, Duke of Edinburgh, whose maternal grandmother was Alexandra's sister Victoria of Hesse.

Similarly to identify Emperor Nicholas II remains his mitochondrial DNA was compared with that of James Carnegie, 3rd Duke of Fife, whose maternal great-grandmother Alexandra of Denmark (Queen Alexandra) was sister of Nicholas II mother Dagmar of Denmark (Empress Maria Feodorovna).

Similarly the remains of king Richard III. 

Human mitochondrial molecular clock

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Human_mitochondrial_molecular_clock 

 

The human mitochondrial molecular clock is the rate at which mutations have been accumulating in the mitochondrial genome of hominids during the course of human evolution. The archeological record of human activity from early periods in human prehistory is relatively limited and its interpretation has been controversial. Because of the uncertainties from the archeological record, scientists have turned to molecular dating techniques in order to refine the timeline of human evolution. A major goal of scientists in the field is to develop an accurate hominid mitochondrial molecular clock which could then be used to confidently date events that occurred during the course of human evolution.

Estimates of the mutation rate of human mitochondrial DNA (mtDNA) vary greatly depending on the available data and the method used for estimation. The two main methods of estimation, phylogeny based methods and pedigree based methods, have produced mutation rates that differ by almost an order of magnitude. Current research has been focused on resolving the high variability obtained from different rate estimates.

Rate variability

A major assumption of the molecular clock theory is that mutations within a particular genetic system occur at a statistically uniform rate and this uniform rate can be used for dating genetic events. In practice the assumption of a single uniform rate is an oversimplification. Though a single mutation rate is often applied, it is often a composite or an average of several different mutation rates. Many factors influence observed mutation rates and these factors include the type of samples, the region of the genome studied and the time period covered.

Actual vs. observed rates

The rate at which mutations occur during reproduction, the germline mutation rate, is thought to be higher than all observed mutation rates, because not all mutations are successfully passed down to subsequent generations. mtDNA is only passed down along the matrilineal line, and therefore mutations passed down to sons are lost. Random genetic drift may also cause the loss of mutations. For these reasons, the actual mutation rate will not be equivalent to the mutation rate observed from a population sample.

Population size

Population dynamics are believed to influence observed mutation rates. When a population is expanding, more germline mutations are preserved in the population. As a result, observed mutation rates tend to increase in an expanding population. When populations contract, as in a population bottleneck, more germline mutations are lost. Population bottlenecks thus tend to slow down observed mutation rates. Since the emergence of the species homo sapiens about 200,000 years ago, human population have expanded from a few thousand individuals living in Africa to over 6.5 billion all over the world. However, the expansion has not been uniform, so the history of human populations may consist of both bottlenecks and expansions.

Structural variability

The mutation rate across the mitochondrial genome is not uniformly distributed. Certain regions of the genome are known to mutate more rapidly than others. The Hypervariable regions are known to be highly polymorphic relative to other parts of the genome.

The rate at which mutations accumulate in coding and non-coding regions of the genome also differs as mutations in the coding region are subject to purifying selection. For this reason, some studies avoid coding region or synonymous mutations when calibrating the molecular clock. Loogvali et al. (2009) only consider synonymous mutations, they have recalibrated the molecular clock of human mtDNA as 7990 years per synonymous mutation over the mitochondrial genome.  Soares et al. (2009) consider both coding and non-coding region mutations to arrive at a single mutation rate, but apply a correction factor to account for selection in the coding region.

Temporal variability

The mutation rate has been observed to vary with time. Mutation rates within the human species are faster than those observed along the human-ape lineage. The mutation rate is also thought to be faster in recent times, since the beginning of the Holocene 11,000 years ago.

Parallel mutations and saturation

Parallel mutation (sometimes referred to as Homoplasy) or convergent evolution occurs when separate lineages have the same mutation independently occur at the same site in the genome. Saturation occurs when a single site experiences multiple mutations. Parallel mutations and saturation result in the underestimation of the mutation rate because they are likely to be overlooked.

Heteroplasmy

Individuals affected by heteroplasmy have a mixture of mtDNA types, some with new mutations and some without. The new mutations may or may not be passed down to subsequent generations. Thus the presence of heteroplasmic individuals in a sample may complicate the calculation of mutation rates.

Methods

Pedigree based

Pedigree methods estimate the mutation rate by comparing the mtDNA sequences of a sample of parent/offspring pairs or analyzing mtDNA sequences of individuals from a deep-rooted genealogy. The number of new mutations in the sample is counted and divided by the total number of parent-to-child DNA transmission events to arrive at a mutation rate.

Phylogeny based

Phylogeny based methods are estimated by first reconstructing the haplotype of the most recent common ancestor (MRCA) of a sample of two or more genetic lineages. A requirement is that the time to the most recent common ancestor (TMRCA) of the sample of lineages must already be known from other independent sources, usually the archeological record. The average number of mutations that have accumulated since the MRCA is then computed and divided by the TMRCA to arrive at the mutation rate. The human mutation rate is usually estimated by comparing the sequences of modern humans and chimpanzees and then reconstructing the ancestral haplotype of the chimpanzee-human common ancestor. According to the paleontological record the last common ancestor of humans may have lived around 6 million years ago.

Pedigree vs. phylogeny comparison

Rates obtained by pedigree methods are about 10 times faster than those obtained by phylogenetic methods. Several factors acting together may be responsible for this difference. As pedigree methods record mutations in living subjects, the mutation rates from pedigree studies are closer to the germline mutation rate. Pedigree studies use genealogies that are only a few generations deep whereas phylogeny based methods use timescales that are thousands or millions of years deep. According to Henn et al. 2009, phylogeny based methods take into account events that occur over long time scales and are thus less affected by stochastic fluctuations. Howell et al. 2003 suggests that selection, saturation, parallel mutations and genetic drift are responsible for the differences observed between pedigree based methods and phylogeny based methods.

Estimating based on AMH archaeology

Methods/parameters for archaeologically estimated dates of mitochondrial Eve

Study	Sequence type	TAnchor (location)	Referencing method (correction method)
Cann, Stoneking & Wilson (1987)	Restriction fragments	40, 30, and 12 Ka (Australia, New Guinea New World)	archaeologically defined migrations matched with estimated sequence divergence rates
Endicott & Ho (2008)	Genomic	40 to 55 Ka (Papua New Guinea) 14.5 to 21.5 Ka (Haps H1 and H3)	PNG following Haplogroup P

Anatomical modern humans (AMH) spread out of Africa and over a large area of Eurasia and left artifacts along the northern coast of the Southwest, South, Southeast and East Asia. Cann, Stoneking & Wilson (1987) did not rely on a predicted T_CHLCA to estimate single-nucleotide polymorphism (SNP) rates. Instead, they used evidence of colonization in Southeast Asia and Oceania to estimate mutation rates. In addition they used RFLP technology (Restriction fragment length polymorphism) to examine differences between DNA. Using these techniques this group came up with a T_MRCA of 140,000 to 290,000 years. Cann et al. (1987) estimated the TMRCA of humans to be approximately 210 ky and the most recent estimates Soares et al. 2009 (using 7 million year chimpanzee human mtDNA MRCA) differ by only 9%, which is relatively close considering the wide confidence range for both estimates and calls for more ancient T_CHLCA. 

Endicott & Ho (2008) have reevaluated the predicted migrations globally and compared those to the actual evidence. This group used the coding regions of sequences. They postulate that the molecular clock based on chimp-human comparisons is not reliable, particularly in predicting recent migrations, such as founding migrations into Europe, Australia, and the Americans. With this technique this group came up with a T_MRCA of 82,000 to 134,000 years.

Estimating based on CHLCA

Because chimps and humans share a matrilineal ancestor, establishing the geological age of that last ancestor allows the estimation of the mutation rate. The chimp-human last common ancestor (CHLCA) is frequently applied as an anchor for mt-T_MRCA studies with ranges between 4 and 13 million years cited in the literature. This is one source of variation in the time estimates. The other weakness is the non-clocklike accumulation of SNPs, would tend to make more recent branches look older than they actually are.

SNP rates as described by Soares et al. (2009)

Regions(s)	Subregions (or site within codon)	SNP rate (per site * year)
Control region	HVR I	1.6 × 10−7
	HVR II	2.3 × 10−7
	remaining	1.5 × 10−8
Protein- coding	(1st and 2nd)	8.8 × 10−9
	(3rd)	1.9 × 10−8
DNA encoding rRNA (rDNA)		8.2 × 10−9
DNA encoding tRNA (tDNA)		6.9 × 10−9
other		2.4 × 10−8
TCHLCA assumed 6.5 Ma, relative rate to 1st & 2nd codons

These two sources may balance each other or amplify each other depending on the direction of the T_CHLCA error. There are two major reasons why this method is widely employed. First the pedigree based rates are inappropriate for estimates for very long periods of time. Second, while the archaeology anchored rates represent the intermediate range, archaeological evidence for human colonization often occurs well after colonization. For example, colonization of Eurasia from west to east is believed to have occurred along the Indian Ocean. However, the oldest archaeological sites that also demonstrate anatomically modern humans (AMH) are in China and Australia, greater than 42,000 years in age. However the oldest Indian site with AMH remains is from 34,000 years, and another site with AMH compatible archaeology is in excess of 76,000 years in age. Therefore, application of the anchor is a subjective interpretation of when humans were first present.

A simple measure the sequence divergence between humans and chimps can be bound by observing the SNPs. Given that the mitogenome is about 16553 base pairs in length (each base-pair which can be aligned with known references is called a site), the formula is:

${\displaystyle rate={\frac {SNPs}{(2T_{CHLCA}16553)}}}$

The '2' in the denominator is derived from the 2 lineages, human and chimpanzee, that split from the CHLCA. Ideally it represents the accumulation of mutations on both lineages but in different positions (SNPs). As long as the number of SNP observed approximates the number of mutations this formula works well. However, at rapidly evolving sites mutations are obscured by saturation affects. Sorting positions within the mitogenome by rate and compensating for saturation are alternative approaches.

Because the T_CHLCA is subject to change with more paleontological information, the equation described above allows the comparison of TMRCA from different studies.

Methods/parameters for estimating date of mitochondrial Eve

Study	Sequence type	TCHLCA (sorting time)	Referencing method (correction method)
Vigilant et al. (1991)	HVR	4 to 6 Ma	CH transversions, (15:1 transition:transversion)
Ingman et al. (2000)	genomic (not HVR)	5 Ma	CH genomic comparison
Endicott & Ho (2008)	genomic (not HVR)	5 to 7.5 Ma	CH (relaxed rate, rate-class defined)
Gonder et al. (2007)	genomic (not HVR)	6.0 Ma (+ 0.5 Ma)	CH (rate class defined)
Mishmar et al. (2003)	genomic (not HVR)	6.5 Ma (+ 0.5 Ma)	CH (rate class defined)
Soares et al. (2009)	genomic	6.5Ma (+ 0.5 Ma)	CHLCA anchored, (Examined selection by Ka/(Ks + k))
Chimpanzee to Human = CH, LCA = last common ancestor

Early, HVR, sequence-based methods

To overcome the effects of saturation, HVR analysis relied on the transversional distance between humans and chimpanzees. A transition to transversion ratio was applied to this distance to estimate sequence divergence in the HVR between chimpanzees and humans, and divided by an assumed T_CHLCA of 4 to 6 million years. Based on 26.4 substitutions between chimpanzee and human and 15:1 ratio, the estimated 396 transitions over 610 base-pairs demonstrated sequence divergence of 69.2% (rate * T_CHLCA of 0.369), producing divergence rates of roughly 11.5% to 17.3% per million years.

HVR is exceptionally prone to saturation, leading to the underestimation of the SNP rate when comparing very distantly related lineages

Vigilant et al. (1991) also estimated the sequence divergence rate for the sites in the rapidly evolving HVR I and HVR II regions. As noted in the table above, the rate of evolution is so high that site saturation occurs in direct chimpanzee and human comparisons. Consequently, this study used transversions, which evolve at a slower rate than the more common transition polymorphisms. Comparing chimp and human mitogenomes, they noted 26.4 transversions within the HVR regions, however they made no correction for saturation. As more HVR sequence was obtained following this study, it was noted that the dinucleotide site CRS:16181-16182 experienced numerous transversions in parsimony analysis, many of these were considered to be sequencing errors. However the sequencing of Feldhofer I Neanderthal revealed that there was also a transversion between humans and Neanderthals at this site. In addition, Soares et al. (2009) noted three sites in which recurrent transversions had occurred in human lineages, two of which are in HVR I, 16265 (12 occurrences) and 16318(8 occurrences). Therefore, 26.4 transversions was an underestimate of the likely number of transversion events. The year 1991 study also used a transition-to-transversion ratio from the study of old world monkeys of 15:1. However, examination of chimp and gorilla HVR reveals a rate that is lower, and the examination of humans places the rate at 34:1. Therefore, this study underestimated that level of sequence divergence between chimpanzee and human. The estimated sequence divergence 0.738/site (includes transversions) is significantly lower than the ~2.5 per site suggested by Soares et al. (2009). These two errors would result in an overestimate of the human mitochondrial TMRCA. However, they failed to detect the basal L0 lineage in the analysis and also failed to detect recurrent transitions in many lineages, which also underestimate the TMRCA. Also, Vigilant et al. (1991) used a more recent CHLCA anchor of 4 to 6 million years.

Coding region sequence based methods

African mtDNA haplogroups

L0   L0d       L0k       L0f       L0b     L0a               L1   L1b     L1c       L5         L2       L6       L3     L4

Partial coding region sequence originally supplemented HVR studies because complete coding region sequence was uncommon. There were suspicions that the HVR studies had missed major branches based on some earlier RFLP and coding region studies. Ingman et al. (2000) was the first study to compare genomic sequences for coalescence analysis. Coding region sequence discriminated M and N haplogroups and L0 and L1 macrohaplogroups. Because the genomic DNA sequencing resolved the two deepest branches it improved some aspects estimating TMRCA over HVR sequence alone. Excluding the D-loop and using a 5-million-year T_CHLCA, Ingman et al. (2000) estimated the mutation rate to be 1.70 × 10⁻⁸ per site per year (rate * T_CHLCA = 0.085, 15,435 sites).

However, coding region DNA has come under question because coding sequences are either under purifying selection to maintain structure and function, or under regional selection to evolve new capacities. The problem with mutations in the coding region has been described as such: mutations occurring in the coding region that are not lethal to the mitochondria can persist but are negatively selective to the host; over a few generations these will persist, but over thousands of generations these slowly are pruned from the population, leaving SNPs. However, over thousands of generations regionally selective mutations may not be discriminated from these transient coding region mutations. The problem with rare mutations in the human mitogenomes is significant enough to prompt a half-dozen recent studies on the matter. 

Ingman et al. (2000) estimated the non-D loop region evolution 1.7 × 10⁻⁸ per year per site based on 53 non-identical genomic sequence overrepresenting Africa in a global sample. Despite this over-representation, the resolution of the L0 subbranches was lacking and one other deep L1 branches has been found. Despite these limitations that sampling was adequate for the hallmark study. Today, L0 is restricted to African populations, whereas L1 is the ancestral haplogroup of all non-Africans, as well as most Africans. Mitochondrial Eve's sequence can be approximated by comparing a sequence from L0 with a sequence from L1. By reconciling the mutations in L0 and L1. The mtDNA sequences of contemporary human populations will generally differ from Mitochondrial Eve's sequence by about 50 mutations. Mutation rates were not classified according to site (other than excluding the HVR regions). The T_CHLCA used in the year 2000 study of 5 Ma was also lower than values used in the most recent studies.

Estimates from ancient DNA

Since it has become possible to sequence large numbers of ancient mitogenomes, several studies have estimated the mitochondrial mutation rate by measuring how many more mutations on average have accumulated in modern (or later) genomes compared to ancient (or earlier) ones descending from the same phylogenetic node. These studies have obtained similar results: central estimates for the whole chromosome, in substitutions per site per year: 2.47 × 10⁻⁸; 2.14 × 10⁻⁸; 2.53 × 10⁻⁸; and 2.74 × 10⁻⁸.

Inter-comparing rates and studies

Molecular clocking of mitochondrial DNA has been criticized because of its inconsistent molecular clock. A retrospective analysis of any pioneering process will reveal inadequacies. With mitochondrial the inadequacies are the argument from ignorance of rate variation and overconfidence concerning the T_CHLCA of 5 Ma. Lack of historical perspective might explain the second issue, the problem of rate variation is something that could only be resolved by the massive study of mitochondria that followed. The number of HVR sequences that have accumulated from 1987 to 2000 increased by magnitudes. Soares et al. (2009) used 2196 mitogenomic sequences and uncovered 10,683 substitution events within these sequences. Eleven of 16560 sites in the mitogenome produced greater than 11% of all the substitutions with statistically significant rate variation within the 11 sites. They argue that there is a neutral-site mutation rate which is a magnitude slower than rate observed for the fastest site, CRS 16519. Consequently, purifying selection aside, the rate of mutation itself varies between sites, with a few sites much more likely to undergo new mutations relative to others. Soares et al. (2009) noted two spans of DNA, CRS 2651-2700 and 3028-3082, that had no SNPs within the 2196 mitogenomic sequences.