Question

Assume that (b) is dominant and (b) is recessive: bb mates with bb. What will be the phenotype of all the offspring?

1) All the offspring will show the dominant trait
2) All the offspring will show the recessive trait
3) Half of the offspring will show the dominant trait and half will show the recessive trait
4) Cannot be determined

Answer 1

When true-breeding individuals with dominant and recessive traits are crossed, all the F2 offspring will exhibit a 3:1 ratio of dominant to recessive traits.

Step-by-step explanation:

When true-breeding or homozygous individuals that differ for a certain trait are crossed, all of the offspring will be heterozygotes for that trait. If the traits are inherited as dominant and recessive, the F₁ offspring will all exhibit the same phenotype as the parent homozygous for the dominant trait. If these heterozygous offspring are self-crossed, the resulting F₂ offspring will be equally likely to inherit gametes carrying the dominant or recessive trait, giving rise to offspring of which one quarter are homozygous dominant, half are heterozygous, and one quarter are homozygous recessive. Because homozygous dominant and heterozygous individuals are phenotypically identical, the observed traits in the F₂ offspring will exhibit a ratio of three dominant to one recessive.