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Red-haired woman

Red-haired woman (mihailomilovanovic, iStockphoto)

STEM in Context

The Chemistry of Redheads

Let's Talk Science
Format
Video Text Images
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7.29
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Summary

Learn how chemistry and genetics makes redheads stand out from the crowd.

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.

Layers of skin cells showing locations of keratinocytes, melanosomes, and melanocytes for dark skin and light skin
Layers of skin cells showing locations of keratinocytes, melanosomes, and melanocytes for dark skin and light skin (Let’s Talk Science based on an image by OpenStax College [CC BY 3.0] via Wikimedia Commons).

 

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 MC1R gene. When the protein is activated, it specifically produces pheomelanin. Redheads have a genetic variant of the MC1R gene 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 MR1C gene is located on chromosome 16
The MR1C gene is located on chromosome 16 (Source: National Center for Biotechnology Information, U.S. National Library of Medicine [public domain] via Wikimedia Commons).

 

The MC1R gene 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 MC1R gene. 

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

Punnett squares showing the potential hair colours of children with parents who do and do not carry the recessive alleles for the trait of red hair
Punnett squares showing the potential hair colours of children with parents who do and do not carry the recessive alleles for the trait of red hair (© 2019 Let’s Talk Science).

 

Image - Text Version

RR does not carry or express the allele for red hair.
Rr carries but does not express the allele for red hair.
rr expresses the allele for red hair.

 

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. 

The Chemistry of Redheads (2017) by Reactions from the American Chemical Society (3:03 min.).

 

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!

Starting Points

Connecting and Relating

  • Do you get sunburnt more quickly than some of your friends? If so, why do you think this is the case?

  • Would you like to have a different hair colour than the colour you were born with? Why/why not?

  • Do you have red hair, or is red hair a common trait in your family?  If so, what comments do people make to you about your hair colour and/or skin tone? 

Connecting and Relating

  • Do you get sunburnt more quickly than some of your friends? If so, why do you think this is the case?

  • Would you like to have a different hair colour than the colour you were born with? Why/why not?

  • Do you have red hair, or is red hair a common trait in your family?  If so, what comments do people make to you about your hair colour and/or skin tone? 

Relating Science and Technology to Society and the Environment

  • Why are some recessive genes expressed in abundance in some geographical areas but not in others? Explain.

  • What are the potential environmental risks of being born with red hair? What are the hereditary risks that may be associated with red hair? Are there any social risks or benefits to having red hair? Explain.  

  • Should scientists try to find a way to increase the production of eumelanin in redheads? Why/why not?

  • Should resources for genetics research be directed to finding a way to manipulate the genes that are passed on to unborn children who will inherit the genes for developing such things as red hair? Why/why not?

Relating Science and Technology to Society and the Environment

  • Why are some recessive genes expressed in abundance in some geographical areas but not in others? Explain.

  • What are the potential environmental risks of being born with red hair? What are the hereditary risks that may be associated with red hair? Are there any social risks or benefits to having red hair? Explain.  

  • Should scientists try to find a way to increase the production of eumelanin in redheads? Why/why not?

  • Should resources for genetics research be directed to finding a way to manipulate the genes that are passed on to unborn children who will inherit the genes for developing such things as red hair? Why/why not?

Exploring Concepts

  • What are eumelanin and pheomelanin? How do they differ? 

  • Explain how gene variation affects the production of eumelanin and pheomelanin.

  • What gene is responsible for red hair? What is required genetically for the trait of red hair to be expressed? 

  • What cells and cellular structures contribute to your skin and hair colour? 

  • Considering your own hair color, what are the possible chances of your child having red hair if the other parent has red hair? Explain.

  • Why does the narrator in the video say that if both parents are redheads they have “almost” a 100% chance of having a redheaded child? What could account for less than 100% chance? Explain.

Exploring Concepts

  • What are eumelanin and pheomelanin? How do they differ? 

  • Explain how gene variation affects the production of eumelanin and pheomelanin.

  • What gene is responsible for red hair? What is required genetically for the trait of red hair to be expressed? 

  • What cells and cellular structures contribute to your skin and hair colour? 

  • Considering your own hair color, what are the possible chances of your child having red hair if the other parent has red hair? Explain.

  • Why does the narrator in the video say that if both parents are redheads they have “almost” a 100% chance of having a redheaded child? What could account for less than 100% chance? Explain.

Nature of Science/Nature of Technology

  • Conduct demographic research on hair color and geography. For example, compare the number of redheads living in Ireland to the number of redheads living in Canada. Explain the difference in terms of genetic inheritance and recessive genes.

Nature of Science/Nature of Technology

  • Conduct demographic research on hair color and geography. For example, compare the number of redheads living in Ireland to the number of redheads living in Canada. Explain the difference in terms of genetic inheritance and recessive genes.

Media Literacy

  • Over the years, has the media changed the way in which they represent people with red hair? Explain.

  • Are there any notable story characters or TV characters you can think of  that have red hair? Do you think their hair colour is an important part of their character? How so? 

Media Literacy

  • Over the years, has the media changed the way in which they represent people with red hair? Explain.

  • Are there any notable story characters or TV characters you can think of  that have red hair? Do you think their hair colour is an important part of their character? How so? 

Teaching Suggestions

  • This article and video can be used to support teaching and learning of Health. Biology and Anatomy related to cell biology, heredity and protein synthesis. Concepts introduced include genetics, pigmentation, pigments, melain, melanocytes, melanosomes, keratinocytes, keratin cells, eumelanin, pheomelanin, protein, gene, variant, recessive, expressed, allele and carrier. 

  • Before reading this article and viewing the video, teachers could provide students with a Vocabulary Preview learning strategy to help engage prior knowledge and introduce new terminology. Ready-to-use Vocabulary Preview reproducibles for this article are available in [Google doc] and [PDF] formats. 

  • This article could be used at the end of a genetics unit as a way to summarize some of the topics covered. Teachers could show the video and have students identify the key points using what they have learned about genetics.

  • Teachers could also use this video to introduce the topic of cancer and risk factors associated with cancer. After viewing, the teacher could lead a class discussion using a question such as one related to the relationships between skin tone, geography, travel and the possibility of increased cancer rates; or a question asking students their opinion on genetic research to remove this characteristic (i.e., red hair and fair skin) from the human genome.

  • To conclude and consolidate learning, teachers could have students complete an Exit Slip learning strategy. Download ready-to-use  Exit Slip reproducibles for this article in [Google doc] or [PDF] formats.

Thank you to Beverly Wiltshire for providing content for these Starting Points.

Teaching Suggestions

  • This article and video can be used to support teaching and learning of Health. Biology and Anatomy related to cell biology, heredity and protein synthesis. Concepts introduced include genetics, pigmentation, pigments, melain, melanocytes, melanosomes, keratinocytes, keratin cells, eumelanin, pheomelanin, protein, gene, variant, recessive, expressed, allele and carrier. 

  • Before reading this article and viewing the video, teachers could provide students with a Vocabulary Preview learning strategy to help engage prior knowledge and introduce new terminology. Ready-to-use Vocabulary Preview reproducibles for this article are available in [Google doc] and [PDF] formats. 

  • This article could be used at the end of a genetics unit as a way to summarize some of the topics covered. Teachers could show the video and have students identify the key points using what they have learned about genetics.

  • Teachers could also use this video to introduce the topic of cancer and risk factors associated with cancer. After viewing, the teacher could lead a class discussion using a question such as one related to the relationships between skin tone, geography, travel and the possibility of increased cancer rates; or a question asking students their opinion on genetic research to remove this characteristic (i.e., red hair and fair skin) from the human genome.

  • To conclude and consolidate learning, teachers could have students complete an Exit Slip learning strategy. Download ready-to-use  Exit Slip reproducibles for this article in [Google doc] or [PDF] formats.

Thank you to Beverly Wiltshire for providing content for these Starting Points.

Learn more

Science Shows Redheads Have Genetic Superpowers (2017)

Article from the NY Post by Suzannah Cahalan including facts about redheads and information about the studies linked to these findings. 

What Causes Sunburns? (2015)

Video (2:33 min.) from SciShow explaining UV radiation, how melanocytes react to protect you from this radiation, and how too much radiation can lead to sunburns. 

References

BBC News (2018, December 11) Gene study unravels redheads mystery

Lefler, L. (2018, October 3). Redheads: The genetics of hair color. Owlcation.

Nasr, S. L. (2008, July 15). How albinism works. HowStuffWorks.

Sobell, J. M. (2001, August 6). What happens when you get a sunburn? Scientific American.

Starr, B. (2012, November 27). Hair color. The Tech Interactive.

U.S. National Library of Medicine. (2019, July 16). MC1R gene.