Understanding Phenotypic Ratios in Genetic Crosses

In which situation are the phenotypes of F2 offspring expected to follow the ratio of 9:3:3:1?

a. A monohybrid cross for 2 unlinked traits

b. A monohybrid cross for 2 closely linked traits

c. A dihybrid cross for 2 unlinked traits

d. A dihybrid cross for 2 closely linked traits

Answer: C, dihybrid cross of 2 unlinked traits.

Explanation: The phenotypic ratio of 9:3:3:1 is achieved in a dihybrid cross involving two unlinked traits. For example, a dihybrid cross involving two different colors and two different shapes of fruit, such as green and yellow, round and wrinkled.

Can you provide an example of a dihybrid cross involving two unlinked traits that would result in a phenotypic ratio of 9:3:3:1?

In a dihybrid cross between pea plants that are heterozygous for seed color (Yy) and seed shape (Rr), the phenotypic ratio of the F2 offspring would be 9:3:3:1. The possible offspring phenotypes would be Yellow Round (YYRR), Yellow Wrinkled (YYrr), Green Round (yyRR), and Green Wrinkled (yyrr).