Chapter 18, Problem 21P

In Problem 5 in Chapter 17, you saw that a SNP located in a hair follicle enhancer of the human KITLG gene is associated with the difference between blond and dark hair. People with blond hair have a high probability of having the A allele, while dark-haired people tend to have the G allele of the SNP.

a.

The information given does not prove that the A allele of the SNP causes blond hair. Explain.

b.

The hair follicle enhancer DNA sequences of the human and mouse KITLG genes are extremely similar; the mouse enhancer normally has the G allele of the SNP. Design a knockin experiment in mice that could test whether or not the SNP allele associated with blondness in humans actually contributes to the blond hair phenotype. Diagram any construct you would use to set up your experiment. (Assume that the A and G alleles are incompletely dominant.)