The Chemistry of Redheads (2024)

STEM Explained

Red-haired woman (mihailomilovanovic, iStockphoto)

Red-haired woman (mihailomilovanovic, iStockphoto)

Biology, Anatomy, Health

Curriculum Alignment

Have you ever wondered why some people have red hair? Well, there’s actually some really cool chemistry and genetics behind being a redhead!

What causes red hair?

First of all, people with red hair have different pigmentation than people with other hair colours. Pigmentation refers to the chemical pigments that give your hair and skin their colour.

The chemical pigment responsible for hair and skin colour is called melanin. Cells called melanocytes use instructions from your DNA to create melanin. They create melanin in protein clusters called melanosomes.

After the melanin is produced, it is transported to keratinocytes. Those are barrier cells at the top layer of the skin. This gives skin its colour. At the base of hair follicles, melanosomes bond with the keratin cells that produce hair. This is what gives hair its colour.

There are two types of human melanin: eumelanin and pheomelanin. Eumelanin ranges from brown to black in colour. Pheomelanin ranges from red to pink.

Redheads have much more pheomelanin than eumelanin in their bodies. That’s why their skin tone is often so light, and why their hair is often reddish.

What are the genetics behind red hair?

Why do redheads have so much pheomelanin? This abundance has a genetic origin. Melanocyte cells contain a protein called the melanocortin 1 receptor. This protein sits on the surface of melanocyte cells. The code for this protein is on the MC1Rgene. When the protein is activated, it specifically produces pheomelanin. Redheads have a genetic variant of the MC1Rgene that causes their melanocytes to primarily produce pheomelanin. However, a study published in 2018 has lead scientists to believe that there many be a number of other genes associated with pheomelanin that controls hair colour.

The MC1Rgene is a recessive gene. Genetically, this means that a few different factors have to come into play for a person to have red hair.

When a gene is recessive, a person must have two copies of the recessive gene in order for the trait to be expressed (or “seen”). Each copy of a gene is called an allele.

A recessive allele can be expressed in two ways. If both parents express a trait, then their child will also express it.

Did you know?

A major study in 2018 suggests there are at least eight other genes that also affect red-headedness.

A person who has an allele for a trait but doesn’t express the trait is called a carrier. If one parent is a carrier and the other parent expresses the trait, there is a 50% chance that their child will express the trait. If both parents are carriers of the recessive allele, then there is a 25% chance that their child will express the trait. In other words, a set of brown-haired parents can still have a redheaded child, as long as they both carry recessive alleles for the MC1Rgene.

How do you know what traits a child will express? You can figure out the probability using a Punnett square.

Why does your skin have melanin?

Melanin doesn’t just give your skin its colour. It’s also your first line of defense against harmful UV radiation produced by the Sun. Melanin cells absorb the UV radiation and spread it out. That way, it doesn’t damage healthy cells in your body. When exposed to the Sun’s rays, your melanocytes go into melanin-production mode. This is what causes a suntan!

But if you are exposed to too much UV radiation, your melanocytes will begin to die. The scientific term for this process is apoptosis. This will activate proteins and enzymes in the skin called prostaglandins and cytokines. They’re linked to your body’s immune system. They cause your blood vessels to dilate (expand) near the surface of the skin. This is what’s responsible for the red colour and burning sensation associated with having a sunburn. People with higher amounts of pheomelanin are more susceptible to sunburn. Not only that, but this damage can cause skin cancers. People with higher amounts of pheomelanin are more susceptible to these, too.

Did you know?

There are a number of different red hair gene mutations that can result in a range of shades of red hair. Some of these genes also cause pale skin. All of these genes can increase a person’s risk of getting a skin cancer called melanoma.

So now you know what causes red hair. You also know about some of the risks associated with having more pheomelanin than eumelanin. But remember, UV radiation can harm all of us. So no matter what your hair colour is, wear sunscreen!