Question

In guinea pigs, the allele for rough coat (r) is dominant over the allele for smooth coat (r). a heterozygous guinea pig and a homozygous recessive guinea pig are mated. which would be the phenotypes of the offspring?
a. all rough coat
b. all smooth coat
c. 2 rough coat and 2 smooth coat
d. 3 rough coat and 1 smooth coat

Answer 1

I believe the answer is A. 

Answer 2

Answer:

The genotypes of the parents are Rr and rr. The possible genotypes (and their phenotypes) are: RR (rough coat), Rr (rough coat), and rr (smooth coat). In a cross of rough coat boar (RR or Rr) and a soft coat sow (rr), there are half of the offspring with the smooth coat. We know that sow must be rr, but the boar can be RR and Rr. If it was RR, all of the offspring would be Rr and would have the rough coat. So, the boar has genotype RR.