Chapter 2, Problem 47P

The following pedigree shows the inheritance of red hair in a family in Scotland. Red hair is caused by homozygosity for a recessive allele of a gene called MC1R. Although worldwide red hair is the rarest of human hair colors, red hair is not uncommon in Scotland. In fact, 40% of Scots without red hair are nonetheless carriers of the red hair allele.

 

a.	Why does red hair show a horizontal inheritance pattern in this particular pedigree even though the trait is caused by a recessive allele?
b.	Assuming that individual III-2 has a child with the Scottish woman shown (III-1) who is not a close relative, what is the probability that this child (IV-1) will have red hair?
c.	What is the probability that the child of first cousins III-9 and III-10 (IV-2) will have red hair?