A simple change in two letters of your DNA can lead to red hair. Two common genetic variants, rs1805007 and rs1805008, are strongly associated with the red hair phenotype in humans. This article will dive into the science behind these variants and explore their role in determining hair color.
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How Does The MC1R Gene Influence Red Hair Development?
The MC1R gene is the most studied human hair color gene on chromosome 16.
It contains instructions to produce a protein called the melanocortin-1 receptor, primarily located on the surface of melanocytes.
Melanocytes are highly differentiated cells that produce a pigment called melanin.
The melanocortin-1 receptor is involved in the pathway that produces melanin.
It controls which kind of melanin is made by melanocytes - eumelanin or pheomelanin.
- People with brown or black hair and dark skin have more eumelanin.
- People with red or blond hair and light skin have more pheomelanin.
When the MC1R gene is mutated, it reduces the ability of the melanocortin-1 receptor to stimulate eumelanin production.
This causes melanocytes to make high levels of pheomelanin.
Because they produce more pheomelanin, people are more likely to develop red hair.
Red hair is closely linked with two changes in the MC1R gene, denoted as rs1805007 and rs1805008.
rs1805007 And rs1805008: What Do These Variants Mean?
The rs1805007 and rs1805008 are the two highly prevalent variants of the MC1R gene.
These variants have been nicknamed ‘R’ alleles to denote their strong association with the red hair color.
The rs1805007 and rs1805008 variants are also known as R151C and R160W, respectively.
The amino acid changes in these variants are Arg151Cys and Arg160Trp.
They make up 22% of the MC1R gene and account for 60% of all cases of red hair.
The Effect Of Different Genotypes
rs1805007
| Genotype | Effect |
| CC | Normal risk for melanoma |
| CT | Carrier of a red hair-associated variant; higher risk of melanoma |
| TT | Increased response to anesthetics; 13-20x higher likelihood of red hair; increased risk of melanoma |
Source: SNPedia
The rs1805007 has been linked to being more responsive to the analgesics pentazocine, nalbuphine, and butorphanol, often used by dentists.
However, redheads carrying this mutation have also demonstrated decreased responsiveness to inhaled general anesthesia desflurane.
rs1805008
| Genotype | Effect |
| CC | Normal risk for melanoma |
| CT | Red hair carrier, higher risk of melanoma |
| TT | ~7-10x higher likelihood of red hair; higher risk of melanoma |
Source: SNPedia
Summary
The genetic variants rs1805007 and rs1805008 are strongly associated with the characteristic red hair color.
These variants impact the production of melanin, the pigment responsible for hair color, and result in the distinctive coloration seen in redheads.
Beyond hair color, these variants have also been linked to other physical traits and health conditions, like melanoma.
While having red hair may not confer any particular advantages or disadvantages in modern society, studying the genetics behind hair color can help us better understand the complex interplay between genetics and physical traits.
As research in this field continues to expand, we may uncover even more insights into the complex genetic landscape of human diversity.
