Suppose that in unicorns, two autosomal loci interact to determine the type of tail. One locus controls whether a tail is present at all. The allele for a tail. T, is dominant over the allele for no tail, t. If a unicorn has a tail, then alleles with an unknown dominance relationship at a second locus determine whether the tail is curly or straight. Define the alleles for tail texture as US for a straight tail and UC for a curly tail.

Farmer Baldridge has two unicorns with curly tails. When he crosses them, one-half of the progeny have curly tails, one-quarter have straight tails, and one-quarter do not have a tail.

What are the genotypes of the parents at the tail-presence gene?

What are the genotypes of the parents at the tail-texture gene?

Place the unicorn genotype or genotypes below each unicorn phenotype in the pedigree below. Some unicorn phenotype in the pedigree below. Some unicorn phenotypes may be the result of more than one genotype.

ooooo tt x tt Tt x tt TTx TT Tt x Tt O TT x tt 00000 USUC XUCUC USUS XUSUS USUS XUCUC UCUC xUCUC USUC XUSUC TT USUS TLUCUC TT USUC I USUS TT UCUC USUC TLUSUS UCUC TLUSUC