The "ginger gene" isn't a single gene, but rather refers to variants (or mutations) in the MC1R gene located on chromosome 16. These variants are primarily responsible for red hair, fair skin, and freckles.
The Role of MC1R
The MC1R gene provides instructions for making a protein called the melanocortin 1 receptor. This receptor sits on the surface of melanocytes, which are cells that produce melanin. Melanin is the pigment that gives skin, hair, and eyes their color. There are two main types of melanin:
- Eumelanin: Produces brown and black pigments.
- Pheomelanin: Produces red and yellow pigments.
Normally, when the melanocortin 1 receptor is activated, it stimulates melanocytes to produce eumelanin. However, when someone has certain variants in their MC1R gene, the receptor doesn't function as efficiently. This leads to:
- Less eumelanin production: Resulting in fair skin and lighter hair.
- More pheomelanin production: Leading to red hair.
How MC1R Variants Cause Red Hair
Individuals with red hair typically inherit two copies of an MC1R variant, one from each parent. Because these variants reduce the receptor's function, pheomelanin production becomes dominant, resulting in the characteristic ginger coloration. If a person only inherits one copy of an MC1R variant, they may not have red hair, but they might have some of the associated traits, such as fair skin or freckles. They also become carriers of the gene.
Other Factors
While MC1R variants are the primary determinant of red hair, other genes can also influence hair color. These genes affect the amount and type of melanin produced, and can modify the expression of red hair.
