Dihybrid crosses can be conducted with two organisms that are heterozygous for two different traits: SsYy x SsYy for example. Which genotypic ratio shows that genes in dihybrid crosses are inherited according to the principle of independent assortment?

Question

A. 25:25:25:25

B. 50:50

C. 3:1

D. 9:3:3:1

Answer 1

The correct answer is D. 9:3:3:1.

In a dihybrid cross such as SsYy x SsYy, where each parent is heterozygous for two traits, the offspring will exhibit a phenotypic ratio of 9:3:3:1. This ratio reflects the principle of independent assortment, which states that the alleles for different traits segregate independently of one another during gamete formation. Thus, you'd expect to see nine offspring with both dominant traits, three with the dominant trait for the first gene and a recessive trait for the second, three with a recessive trait for the first gene and a dominant trait for the second, and one with both recessive traits.