The Genetics of Red Hair – What Causes of Red Hair?

About 1-2% of the human population is red-haired. This makes red hair as the rarest natural color among humans. Genetic mutation in the MC1R gene causes red hair. Find out in this article how MC1R mutation causes red hair and fair skin and how these traits are being inherited. Learn also the medical implication of inheriting the physical traits.

The Cause of Red Hair is Explained by Genetics

Red hair genetics (Image from Wikimedia Commons)Our hair follicles and our skin contain specialized cells called melanocytes. These cells produce the pigment melanin that gives color to hair and skin. There are two types of melanin produced by melanocytes: eumelanin (brown-black pigment) and phaeomelanin (reddish-brown). The skin and hair color of an individual is determined by how much eumelanin or phaeomelanin is produced by the melanocytes. If there is more eumelanin synthesized in a person, he or she will have brown-black hair coloration. On the other hand, higher amount of phaeomelanin produced by melanocytes causes red hair and pale skin.

Eumelanin is produced through the conversion of phaeomelanin to eumelanin in melanocytes. The conversion process occur when the MC1R (melanocortin 1) receptors in the cell membrane of melanocytes receives the signal from the melanocyte-stimulating hormone (MSH). People with black hair have active MC1R receptors that are very responsive to the action of MSH. MC1R receptors are encoded by the MC1R gene located in human chromosome 16. We have two sets of MC1R gene, one from our mom and another from our dad.


Genetic Mutation Causes Red Hair

Mutation of MC1R gene results to the production of melanocortin 1 receptors that are not responsive to MSH. As a result, no eumelanin is produced and there is a build up of phaeomelanin which causes red hair. Persons with red hair are also prone to freckles or brownish patches in the skin.

The mutated version of MC1R gene is considered the recessive gene while the normal copy is the dominant gene (brown-black hair). A person should have two copies of the recessive gene (1 from the mother and another from the father) in order to develop red hair. When a person only possesses one copy of the recessive gene, he or she may not develop red hair but considered a carrier of the gene.

Red-haired Child from Non Red-Haired Parents

You may wonder why there are non red-haired couples who produce children with red hair. This is simply explained by genetics using the concept of autosomal recessive pattern of inheritance. When both the mother and the father carry one copy of the recessive gene, each of their children has 25% chance of developing red hair. The child who becomes red-haired carry the recessive gene of his/her father and of his/her mother. In other words, two copies of the recessive gene are needed to become red-haired.

So now that the genetics of red hair is explained, let us look on the medical implication of possessing the trait.

Red Hair and Skin Cancer

The pale skin of red-haired people has been shown to be highly susceptible to the damaging effects of the sun’s ultraviolet radiation. Researchers have found that UV radiation interacts with phaeomelanin (the abundant pigment in redheads) producing reactive molecules that can damage the DNA, which can lead to a variety of skin cancers such as squamous cell carcinoma, basal cell carcinoma, and melanoma. Redhead people are advised to minimize exposure to the sun or wear sunscreen to prevent skin cancer.[ad#afterpost]