Question

In pea plants P represents purple flowers while p represents white, and T represents tall plants while t represents short. Biologists cross two pea plants, each with the genotype PpTt. We would expect what phenotypic ratio from this dihybrid cross?

A) 1:1:1:1 ratio
B.) 9:3:3:1 ratio
C.) all dominant for both traits
D.) all recessive for both traits

Answer 1

b.) 9:3:3:1 ratio (9 purple, tall / 3 purple, short / 3 white tall / 1 white short)

Answer 2

Answer:

The answer is b) 9:3:3:1 ratio.

Explanation:

This cross follows the ratio expected by Mendel’s law of independent assortment that states genes are independently separated. In this case the two pea plants are called dihybrids because they are formed by two heterozygous Pp for the color of the plants and Tt for the height. According to Mendel the cross two dihybrids would produce four different phenotypic categories with the 9:3:3:1 ratio that in this case is: 9 tall and purple plants, 3 purple and short plants, 3 tall and white plants and 1 short and white plant.