Question

In peas, gray seed color is dominant to white. For the purpose of these questions assume that Mendel crossed plants with gray seeds with each other and the following progeny were produced: 250 gray and 80 white.

A) What is the most probable genotype of each parent?
B) What genotypic and phenotypic ratios are expected in the progeny of such a cross?

Answer 1

The most probable genotype of each parent in the cross involving seed color in peas is GG or Gg for the parent with gray seeds and gg for the parent with white seeds. The expected genotypic ratio in the progeny is 1:2:1, and the expected phenotypic ratio is 3:1.

Step-by-step explanation:

To determine the most probable genotype of each parent in a cross involving seed color in peas, we can use the observed progeny ratios. In this case, the cross produced 250 gray and 80 white seeds. Since gray is dominant to white, the gray seeds must contain at least one dominant allele for seed color. Therefore, the most probable genotype of the parent with gray seeds is GG or Gg. On the other hand, the white seeds can only occur when both alleles for seed color are recessive, so the most probable genotype of the parent with white seeds is gg.

In terms of genotypic and phenotypic ratios expected in the progeny, we can use a Punnett square to analyze the cross between the parents with the most probable genotypes (GG or Gg x gg). When we do this, we find that the expected genotypic ratio is 1:2:1, meaning there is a 25% chance of getting GG, 50% chance of getting Gg, and 25% chance of getting gg offspring. The expected phenotypic ratio is 3:1, meaning there is a 75% chance of getting gray seeds and a 25% chance of getting white seeds.