Expert: Dana Krempels, Ph.D. - 1/2/2010

Question
Question for you.

I know what a widow peak is and that it is dominant. I think it is determined by the autosomal chromosomes but do you know which one? I'm probably wrong but hoping you could clarify for me. Im not sure how a gene like this is inherited.

Thank you.  

Answer
Dear Alex,

The location of the gene encoding the Widow's Peak hairline hasn't been discovered yet.  But if its Mendelian inheritance patterns are an indication, it is located on an autosomal chromosome.  We just don't know which one.  Nor do we know exactly how a single gene can encode something as complex as the pattern of the hairline!

The alleles of the gene are inherited as a simple autosomal trait, with Widow's Peak (W) being the dominant allele (i.e., version of the gene) and straight hairline (w) being recessive.  A person has two copies of the gene, and may have the genotype WW, Ww or ww with respect to the gene.

If you have a Widow's Peak, your genotype is either WW or Ww.  If you have a straight hairline, it's ww.  Inheritance can be determined with a simple Punnett square, inserting any of the possible genotypes to see what the likelihood of the childrens' phenotypes will be.

Hope that helps.

Dana