Genetics of Red Hair
What do Napoleon Bonaparte, Oliver Cromwell, and Thomas Jefferson have in common? Besides the obvious similarity as heads-of-state, all three had red hair.
Hair color ranges from platinum blond to ebony, due to levels of pigments produced by specialized cells called melanocytes. Those with dark hair have cells that produce a pigment called eumelanin, and those with blond or red hair have cells that produce pheomelanin. The relative ratio of eumelanin to pheomelanin determines a person ’s hair color. A complete absence of both pigments leads to white hair color.
The gene responsible for determining hair color is called the Melanocortin 1 Receptor, or MC1R. If the MC1R gene is active, it produces eumelanin and a person will have darker skin and hair. If the MC1R gene does not function (i.e. it is blocked or inactivated), the melanocytes will produce pheomelanin instead of eumelanin. A person with a malfunctioning MC1R gene will have blond or red hair, due to the lack of eumelanin, along with freckles. MC1R gene mutations are seen in all ethnicities.
MC1R Gene Location
The MC1R gene is located on the long arm of chromosome 16. Its official location is 16q24.3, and is 3,098 base pairs in length. Depending on the specific mutation (known as a polymorphism in the language of genetics), hair color will range from strawberry blond to auburn. The MC1R gene encodes a protein made up of 317 amino acids. Over 35 sites on the gene have been identified with polymorphisms, and only a small number of these mutations cause red hair shades.
People with only one allele will have strawberry blond hair rather than bright red hair. Some alleles, such as the V60L gene, result in reduced function of the MC1R gene. As the gene is not completely inactivated, hair color may be auburn or reddish in tint rather than bright red.
How likely am I to Have a Child with Red Hair?
Red hair is recessive, which means a person may have brown hair, and carry the “red gene” without expressing the hair color. A person must have two copies of the recessive gene to express the trait. The chances of having a child with red hair depend on the genes of the parents. For simplicity ’s sake, the various polymorphisms in the MC1R gene will be called the “red hair gene.” The red hair gene will be labeled as a lower case r in the charts below and brown hair will be labeled with an upper case R.
Case 1: Parents with Brown Hair
In the first scenario, two parents have brown hair and do not carry any polymorphisms on the MC1R gene. In other words, neither of the parents is a carrier for the red hair gene. None of their children will have red hair, unless a new mutation arises spontaneously. These parents have almost no chance of having a child with red hair, unless a de novo mutation were to arise.
Case 2: Brown-Haired Carriers
In the second scenario, both parents have brown hair, but carry a red-hair causing gene. These parents are both called “carriers” of the gene. In this case, the parents will have a 25% chance of having a child with brown hair who does not carry the red gene. They have a 50% chance of having a child with brown hair who carries the red gene. There is a 25% chance that the parents will have a child with red hair.
Case 3: Parents with Brown and Red Hair
A third possibility involves a parent with red hair and a parent with brown hair. The parent with brown hair in this case is not a carrier of the red gene. Each of the children will have one allele for the red hair gene, and will be carriers of the gene. None of the children, however, will display the physical trait of having red hair.
Case 4: Parents with Brown Hair (Carrier) and Red Hair
In a fourth scenario, one parent has red hair and the other has brown hair, but is a carrier of the red gene. There is a 50% chance that the children will have red hair, and a 50% chance that the children will be brown-haired carriers of the red gene.
This is the scenario in my own family: I have brown hair and probably do not carry red-causing MC1R polymorphisms. My husband, however, has the classic red hair phenotype. One of my sons is blond, and the other has strawberry blond hair.
Case 5: Parents with Red Hair
The last case includes two parents with red hair: in this situation, all of the children would have the same phenotype as the parents. The children will all have red hair, since neither parent has the dominant “brown hair” MC1R genotype. In some cases, different polymorphisms (alleles) may be inherited from each parent. This scenario is common in locations where red hair is a common occurrence: primarily in Scotland and Ireland.
Famous RedheadsEmily Dickinson, the American poet
Antonio Vivaldi, the Italian composer
Mark Twain, the American author
Malcolm X, civil rights activist
Cleopatra, Egyptian ruler
Vladimir Lenin, Russian revolutionary
Genetic Mutation MC1R: Beyond Hair Color
The MC1R gene is expressed in many cells, and is responsible for more than hair color. MC1R plays a role in inflammatory response, pain sensitivity, and the immune system. The far reaching effects of the MC1R gene are listed below:
Cancer risk
Redheads have an increased risk for melanoma, as the melanocytes in people with red hair do not produce the protective eumelanin pigment. Unfortunately, the risk of cancer is increased even when there is no exposure to sunlight, so those with red hair should have regular check-ups with a dermatologist to monitor any skin changes. It is important to note that people who have dark skin and MC1R mutations are also at risk for skin cancer.
Increased pain sensation
People who have red hair are more sensitive to pain caused by burns and freezing than people with brown hair. Studies performed by Edwin B. Liem at the National Institutes of Health demonstrated an increased sensation of pain caused by thermal changes, and an increased need for anesthetic. Redheads required 19% more anesthetic than their brown haired counterparts. Interestingly, those with red hair demonstrate a reduced sensitivity to stinging pain (the type of pain encountered when receiving an injection). The MC1R gene affects the binding of endorphins, which are the body ’s natural painkillers.
Red Hair Stereotypes and Beliefs
The most common modern stereotype about redheads is that red hair comes with a fiery, feisty personality. Earlier in history, redheads faced more dangerous beliefs about their red hair. In ancient Egypt, redheads were burned alive as a sacrifice to the god Osiris. Their ashes were blown over agricultural fields by winnowing fans and used as fertilizer for the season ’s crops. Early Egyptians regarded red hair as an unlucky trait.
In the middle ages, those with red hair could be labeled as witches or vampires. The Malleus Maleficarum (a report on witches in the Middle Ages) states, “Those whose hair is red, of a certain peculiar shade, are unmistakably vampires.”
Redhead Nicknames
There are various nicknames used around the world for those who have red hair. Sometimes the nicknames are affectionate, but many of the nicknames are used as insults.
Ranga: An Australian nickname for people with red hair. The word is a shortened version of the word orangutan.
Ginger: A name used for redheads, most commonly used in the U.K. The cartoon series South Park satirized the persecution of redheads with a genocidal campaign against “ginger people.”
Carrot Top: A nickname often used in the United States, comparing red hair to the color of carrots.
Koakage: The Japanese word for redheads – the word “akage” indicates the red hair and the prefix “ko” for something small or cute.
Other Causes of Red Hair
Some people do not come by their red hair via the MC1R gene. One type of albinism (type 3, or rufous albinism) demonstrates a phenotype of red hair and ruddy skin. This form of albinism is most common in New Guinea and Africa.
Severe malnutrition can lead to a condition known as kwashiorkor – the deprivation of protein and calories from an individual ’s diet will lead to failure to thrive, edema, excessive hair growth, and depigmentation, along with the development of red hair. The Biblical story of Esau is fascinating in this regard, because the Bible describes Esau as covered in red hair. As the story goes, Esau sold his birthright as the first-born son to his younger twin, in exchange for a bowl of soup. While the story is intended to demonstrate the hazards of placing material desires over a spiritual blessing, one has to wonder if Esau was simply suffering from the effects of kwashiorkor.
Proopiomelanocortin deficiency (POMC) is a genetic disease resulting in obesity, adrenal insufficiency, and red hair. Children with this genetic disorder exhibit early onset severe obesity and striking red hair, due to the effects the POMC gene has on ACTH production and the influence this gene has on the phaeomelanin:eumelanin ratio in cells.
The Myth of Redhead Extinction
News reports reported on the imminent extinction of redheads in August 2007. Like many other myths circulating on the internet, the reports were incorrect. Based on the incorrect assumption that recessive genes will “die out” over time, the news reports stated that the gene for red hair would be gone by the year 2060. The reports supposedly came from the Oxford Hair Foundation, but no such scientific entity exists. The Oxford Hair Foundation manufactures beauty products and is not an academic facility. The claim that redheads are going extinct is completely false: recessive genes may become rare, but will not disappear from the human genome. Red hair will exist well beyond the year 2060!
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