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 of the following would be the percentages of possible offspring phenotypes?
A
100% rough coat
B
100% smooth coat
C
50% rough coat and 50% smooth coat
D
75% rough coat and 25% smooth coat

Answer 1

C — 50% rough coat and 50% smooth coat.

Explanation: Rr × rr gives gametes R or r from the heterozygote and only r from the homozygous recessive. Offspring genotypes are Rr and rr in a 1:1 ratio, so 50% show the dominant rough phenotype and 50% the recessive smooth phenotype.