Answer to Question #319913 in Genetics for G6ix

Question

Consider three yellow, round peas, labeled A, B, and C. Each was grown Into a plant and crossed to a plant grown from a green, wrinkled pea. Exactly 100 peas derived from each cross were sorted into phenotypic classes as follows: A: 51 yellow, round 49 green, round B: 100 yellow, round 24 yellow, round 26 yellow, wrinkled 25 green, round 25 green, wrinkled What are the genotypes of plants A, B, and C?

Answer 1

Suppose that the following genes are responsible for different traits:

A - yellow color;

a - green color;

B - round;

b - wrinkled.

Let's make the cross to find out the genotypes of plants:

P (A): AaBB (yellow, round) + aabb (green, wrinkled)

↓

F1: 51 AaBb (yellow, round) + 49 aaBb (green, round)

P (B): AABB (yellow, round) + aabb (green, wrinkled)

↓

F1: 100 AaBb (yellow, round)

P (C): AaBb (yellow, round) + aabb (green, wrinkled)

↓

F1: 24 AaBb (yellow, round) + 26 Aabb (yellow, wrinkled) + 25 aaBb (green, round) + 25 aabb (green, wrinkled)

First, we marked with a dash the unknown second alleles in each genotype hybridity expressing a dominant trait. Then, by correspondence, we select the genotypes of yellow round peas in parent plants A, B and C (we have already entered them above and highlighted them in bold). After that, of course, we added the genotypes of the offsprings (also above).

Thus, the genotype of plant A is AaBB, the genotype of plant B is AABB, and the genotype of plant C is AaBb.