Question

White feathers in canaries are dominant to yellow feathers. A heterozygous canary is crossed with a homozygous recessive canary. What is the ratio of the offspring that are homozygous to the total number of offspring?

a) 1:1
b) 1:2
c) 2:1
d) 3:1

Answer 1

In the cross between a heterozygous canary and a homozygous recessive canary, the ratio of homozygous offspring to the total number of offspring is 1:2, with one homozygous recessive for every two total offspring.

Step-by-step explanation:

White feathers in canaries being dominant to yellow feathers suggests a simple Mendelian inheritance. A heterozygous canary (Ww) crossed with a homozygous recessive canary (ww) would use a Punnett square to predict the offspring. The genotypes of the possible offspring would be Ww (heterozygous white) and ww (homozygous yellow). Since the question asks for the ratio of homozygous offspring to the total number of offspring, we look at the ww offspring compared to the total. The Punnett square would show a 1:1 ratio of Ww to ww, which means for every 2 offspring, 1 is homozygous recessive. Therefore, the ratio of homozygous (ww) to total offspring (Ww and ww) would be 1:2.