Red Hair Genetics
Since both copies of your MC1R gene need to be the red hair versions (rr) to become a redhead, the following possible situations can result in redheaded offspring:
1. Both parents are carriers. As shown in this punnett square, father (yellow) and mother (pink) contribute one of two possible alleles (R or r) of the MC1R variants to the baby. As a result, there is a 25% chance that any of their child will inherit two r alleles from each parents and will be a redhead.
2. One parent (e.g., mother) is a redhead and the father is a carrier. In this case, every child will inherit one r allele from their mother and has an equal chance of inheriting the R or r allele from the father. Therefore, the chance of each child being redheaded is 50/50.
3. If both parents have red hair, then all offspring will be red headed (rr).
If one of the parent does not carry the red hair (r) allele, then no matter what the other parent's genotype (RR, Rr, or rr), none of their children will have red hair. Although some kids will be red hair carriers if they inherit a r allele.
Preserving the Red Hair Trait
The myth that redheads might die off in the near future has drawn considerable attentions. Due to the recessive nature of the red hair r allele, it takes 2 carriers (Rr) to have a red-headed child. With the increase of globalization and inter-ethnic mixing in marriage, it is reasonable to expect that the chance of 2 red hair carriers getting married and bearing children would be declining.
When a red hair carrier marries to a non-carrier, their children are not red headed, but some will carry the red hair r allele. The frequency of the r alleles in the population in fact remains constant. We cannot easily tell if a person is a red hair carrier (Rr) without examining his/her extended family members' hair colors or analyzing his/her MC1R gene. Therefore, it is not possible to get a good estimate of the population of red hair carriers (Rr). However, we can reasonably expect the population of red hair carriers is much greater than that of the redheads. Even though there is no redhead in your immediate family, the chance that you are a carrier (Rr) is still quite high. It is estimated that as many as one in four Caucasians in the US might be a red hair carrier. Our RedTracer DNA Test can help you uncover whether you carry any of the red hair causing variants.