Vanessa has obtained two true-breeding strains of mice, each homozygous for an independently discovered recessive mutation that prevents the formation of hair on the body. One of the mutant strains is called naked, and the other mutation strain is called hairless. To determine whether the two mutations are simply alleles for the same gene, Vanessa crosses naked and hairless mice with each other (cross 1). All the offspring are phenotypically wildtype.
A) What is the most likely explanation for the phenotypes of the F1 mice? Are the naked and hairless mutations alleles for the same gene?
B) Vanessa next intercrosses the F1 mice (cross 2) and based in the F2 phenotype ratios, concludes that there is no gene interaction. Fill out the following information for the F1 intercross and F2 progeny.
Use these symbols: n = naked mutation, N = wild-type Allele, h = hairless mutation, H = wild-type Allele.
Cross 1: parental genotypes:
F1 genotypes:
Cross 2: Write out a Punnett square for the F1 intercross and give the F2 phenotype ratio:
F2 phenotype ratio __________________