Changes

The lack of diversity of the melanocortin 1 receptor (MC1R) alleles in African population suggests that the gain-of-function MC1R variants have been selected for higher eumelanin production. In contrast, dysfunctional variants, found enriched in the population with European ancestry, impair its ability in elevating cAMP levels and tyrosinase expression in melanocytes. As a result, melanocytes carrying the dysfunctional variants produce more pheomelanin, leading to lighter skin and red hair color. The enrichment of these variants is evolutionarily selected in the population living at high-latitude regions to compensate for the reduced vitamin D synthesis due to low sunlight exposure. The red hair phenotype, accompanied by fair skin and freckles in pigmentation, is associated with pheomelanin production. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin.

The lack of diversity of the melanocortin 1 receptor (MC1R) alleles in African population suggests that the gain-of-function MC1R variants have been selected for higher eumelanin production. In contrast, dysfunctional variants, found enriched in the population with European ancestry, impair its ability in elevating cAMP levels and tyrosinase expression in melanocytes. As a result, melanocytes carrying the dysfunctional variants produce more pheomelanin, leading to lighter skin and red hair color. The enrichment of these variants is evolutionarily selected in the population living at high-latitude regions to compensate for the reduced vitamin D synthesis due to low sunlight exposure. The red hair phenotype, accompanied by fair skin and freckles in pigmentation, is associated with pheomelanin production. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin.

The genetics of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. Eighty percent of redheads have an MC1R gene variant.

The genetics of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. Eighty percent of redheads have an MC1R gene variant.

Red hair is associated with fair skin color because low concentrations of eumelanin throughout the body of those with red hair caused by a MC1R mutation can cause both. The lower melanin concentration in skin confers the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions. However, when UV-radiation is strong (as in regions close to the equator) the lower concentration of melanin leads to several medical disadvantages, such as a higher risk of skin cancer. The MC1R variant gene that gives people red hair generally results in skin that is difficult or impossible to tan. Because of the natural tanning reaction to the sun's ultraviolet light and high amounts of pheomelanin in the skin, freckles are a common but not universal feature of red-haired people.

Red hair is associated with fair skin color because low concentrations of eumelanin throughout the body of those with red hair caused by a MC1R mutation can cause both. The lower melanin concentration in skin confers the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions.  

Red hair can originate from several changes on the MC1R-gene. If one of these changes is present on both chromosomes then the respective individual is likely to have red hair. This type of inheritance is described as an autosomal recessive. Even if both parents do not have red hair themselves, both can be carriers for the gene and have a redheaded child.

 

UV radiation is the strongest near the equator because ozone in these areas is naturally thinner, so there is less to absorb the UV radiation. In this case when the human redhead has a lower concentration of melanin, while living or being exposed near Earth's equator, can lead to multiple disadvantages medically, with skin cancer being at an extremely high risk. Although in much more rare occasions, some humans do not come by their red hair via the MC1R gene, the MC1R variant gene that typically helps produce red hair generally results in a fairer skin that is difficult or impossible to tan. As a result of the natural tanning reaction to the sun's ultraviolet light and high amounts of pheomelanin in the skin, freckles on the pale skin are a common and an inherited characteristic of hyper-pigmentation, but not always a universal feature of red-haired people.

Culturally natural red hair typically originates from Celtic, Scottish, and Irish origins accompanied by very white skin. The red hair color can originate from several changes on the MC1R-gene. If one of these changes is present on both chromosomes then the respective individual is likely to have red hair. This type of inheritance is described as an autosomal recessive. According to a a study in 2001 by, [[Oxford University]], in almost all families MC1R alleles behave as normal recessive mutations, although there are a few rare human individuals with red hair in whom no MC1R variant can be found. Even if both parents do not have red hair themselves, both can be carriers for this MC1R-gene and have a child with red hair.

 

Genetic studies of dizygotic (fraternal) twins indicate that the MC1R gene is not solely responsible for the red hair phenotype; unidentified modifier genes exist, making variance in the MC1R gene necessary, but not sufficient, for red hair production.

Genetic studies of dizygotic (fraternal) twins indicate that the MC1R gene is not solely responsible for the red hair phenotype; unidentified modifier genes exist, making variance in the MC1R gene necessary, but not sufficient, for red hair production.

The pigment pheomelanin gives red hair its distinctive color. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin.

The pigment pheomelanin gives red hair its distinctive color. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin.

The [[genetics]] of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. Eighty percent of redheads have an MC1R gene variant. Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans.  

The [[genetics]] of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. Eighty percent of redheads have an MC1R gene variant. Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans.  

Red hair is associated with fair skin color because low concentrations of eumelanin throughout the body of those with red hair caused by a MC1R mutation can cause both. The lower melanin concentration in skin confers the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions. However, when UV-radiation is strong (as in regions close to the equator) the lower concentration of melanin leads to several medical disadvantages, such as a higher risk of skin cancer. The MC1R variant gene that gives people red hair generally results in skin that is difficult or impossible to sun tan. Because of the natural tanning reaction to the sun's ultraviolet light and high amounts of pheomelanin in the skin, freckles are a common but not universal feature of red-haired people.

Red hair is associated with fair skin color because low concentrations of eumelanin throughout the body of those with red hair caused by a MC1R mutation can cause both. The lower melanin concentration in skin confers the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions. Additionally red hair doesn’t gray in color as much as other hair colors. As the human gets older, their red hair initially tends to turn blond and then white.

Red hair can originate from several changes on the MC1R-gene. If one of these changes is present on both chromosomes then the respective individual is likely to have red hair. This type of inheritance is described as an autosomal [[recessive gene|recessive]]. Even if both parents do not have red hair themselves, both can be Genetic carriers for the gene and have a redheaded child.

Genetic studies of dizygotic (fraternal) twins indicate that the MC1R gene is not solely responsible for the red hair phenotype; unidentified modifier genes exist, making variance in the MC1R gene necessary, but not sufficient, for red hair production. Additionally Red hair doesn’t gray as much as other hair colors. Red hair initially tends to turn blond and then white.

=== Genetics ===

=== Genetics ===

[[File: Redhead_close_up.jpg|thumb| A close-up view of red hair]]

[[File: Redhead_close_up.jpg|thumb| A close-up view of red hair]]

Red hair is caused by a relatively rare recessive allele (variant of a gene), the expression of which can skip generations.

Red hair is caused by a relatively rare recessive allele (variant of a gene), the expression of which can skip generations.

Red hair is the rarest natural hair color in humans. The non-tanning skin associated with red hair may have been advantageous in far-northern climates where sunlight is scarce.

Red hair is the rarest natural hair color in humans. The non-tanning skin associated with red hair may have been advantageous in far-northern climates where sunlight is scarce.

== Medical implications of the red hair gene ==

== Medical implications of the red hair gene ==

=== Melanoma ===

=== Melanoma ===