MadSci Network: Genetics

Re: Can two redheads have a non-reheaded child?

Date: Wed Jun 2 13:23:19 2004
Posted By: Jeff Buzby, Scientist, CHOC Research Institute
Area of science: Genetics
ID: 1085621298.Ge

Dear Elayne,

I would 1st like to echo the comment of Evelyn Tsang in answer to a similar question, that "red hair inheritance is a common question here on MadSci". She also provides the following helpful links to other related MadSci Genetics Network responses by Neil Saunders, Carolyn Pettibone, & Michael Onken. Christopher Carlson also presents a very nice, more recent explanation of red hair inheritance, as well.

Your case is a somewhat genetically simpler than most of these examples, however, since both you & your husband are phenotypic redheads. In your case, I think that the most easily understandable explanation can be found in the Red Hair section of the Genotype -> Phenotype Classroom Booklet, from the Woodrow Wilson Biology Institute. I discussed this explanation in answer to a recent related question, too. But in relation to your situation, I think that it's important to realize that; 1) red-hair is actually dominant over blonde hair, & 2) the contribution of darker hair pigment to the hair coloration is genetically separate from the red coloration. As described in the Red Hair tutorial above, if both you & your husband are GG homozygotes for the red hair allele, characterized by "heavy" red coloration, then all of your children would have to inherit a homozygous red hair phenotype, too. The only possible difference might be a variable contribution of the darker pigmentation. If 1 of you carries the "less red", heterozygous Gg genotype, your children would have a 50:50 chance of inheriting either the GG "heavy" or Gg "light" red phenotype. Depending on the contribution of the darker pigmentation, the Gg offspring could have a more auburn than red coloration, but they would still have a red component. However, if both of you are heterozygous Gg redheads, your children would have a 50% chance of also inheriting a Gg genotype, a 25% chance of inheriting a GG homozygous "heavy red" genotype, & a 25% chance of inheriting a gg homozygous non-red genotype. Based on your characterization of you & your husband as "redheads", I would guess that if either of you is a Gg heterozygote, you probably have very little dark pigment contribution, since this would produce a more auburn coloration.

To summarize your most likely possibilities for non-redheaded offspring, if one of you is a Gg heterozygote, your children could have a 50% chance of inheriting a more auburn hair color, but they would probably have to also inherit some darker pigmentation that might be masked from the GG homozygous parent. Your best chance would be if both of you happen to be Gg heterozygotes, in which case any gg homozygous offspring, with a probability of 1:4, would most likely have blonde hair, since neither of you would contribute much dark pigmentation if you have phenotypically red rather than auburn hair. Unfortunately, the phenotypic key to determining you & your husband's red hair genotypes is the rather imprecise estimate of "how red" your hair colors are. I would say that if you both have the classical "flaming red hair" coloration, you are most likely both GG homozygotes with no chance for non-redheaded offspring. However, if 1 or both of you have a more subdued, light-red hair coloration, then you could have a heterogous Gg genotype, with the possibilities for non-redheaded offspring outlined above.

I apologize if this explanation is too technical. On the other hand, if you'd like to see a synopsis of the science behind this overview, you can visit the Red Hair Color entry in the official, Online Mendelian Inheritance in Man (OMIN) database from the Nat'l Center for Biotechnology Info., as cited by Carolyn Pettibone above.

So, the short answer to your question is that there might be a chance, depending on "how red" you & your husband's hair colors are...

Jeff Buzby, Ph.D.
CHOC Research Institute
MadSci Genetics Network

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