Genetics Practice

Question

Hello I was hoping someone could help me out with this question I have been practicing on:

1. A pea plant with round seeds is crossed with a pea plant that has wrinkled seeds. For the cross, indicate each of the following:

a) the genotype of each of the parents if the dominant phenotype is heterozygous.

b) What gametes will each parent produce?

c) if two round plants from the F1 generation are crossed, what would be the resulting genotypes and phenotypes of the F2 generation? Provide the Punnett square as well as your answer below.

Answer 1

To start, let's define some alleles/genotypes/phenotypes.

Since plants are diploid, they have two alleles. If R is round and r is wrinkled, there are three different genotypes possible with the following phenotypes:

RR = Round

Rr = Round

rr = wrinkled

For part a), the genotype of the wrinkled parent would have to be rr, and the round parent, if heterozygous, would be Rr.

During meiosis, each diploid plant produces haploid gametes, so the Rr parent would produce 1/2 "R" gametes and 1/2 "r" gametes, while the rr parent only produces "r" gametes.

For part c), you have to understand the the term "F1" implies heterozygotes. With that knowledge, the F1 intercross would be Rr (round) x Rr (round). As in part b) above, the meiosis products would be 1/2 R and 1/2 r for each parent. Is that clear enough to set up the Punnett square? The genotypes would be 1/4 RR, 1/2 Rr (all of these are round, so 3/4 round), and 1/4 rr (wrinkled).

Hope that helps! Feel free to follow up!

Heidi