Question

You cross two true-breeding parents (one with yellow seeds and one with green seeds), grow and self-pollinate the F1 generation, and then count the number of offspring with yellow and green seeds in the F2 generation. If you counted 2,000 offspring and there was a 3:1 ratio of yellow:green seeds, how many offspring would have yellow seeds?

Answer 1

1500

Step-by-step explanation:

Let's assume that the allele for yellow seed color is "Y" and the allele for green seed color is "y". Genotype of pure breeding yellow seeded plant would be "YY" and that of the green seeded plant would be "yy". A cross between YY and yy gives all heterozygous yellow seeded plants (Yy) in F1 progeny. Self pollination of two F1 plants (Yy x Yy) obtains F2 generation in 3 yellow: 1 green ratio.

The total population size of F2 generation = 2000

The proportion of yellow seeded plants in F2 generation = 3/4 (since the F2 phenotype ratio is given 3 yellow: 1 green)

Therefore, total number of yellow seeded plants in F2 progeny = 3/4 x 2000= 1500