Question

A cross between two pea plants, both of which grew from yellow round seeds, gave the following numbers of seeds: 156 yellow round and 54 yellow wrinkled. What are the genotypes of the parent plants? (Yellow and round are dominant traits.)

Answer 1

Answer: The correct answer would be YYRr and Y_Rr

Explanation:

Let us denote Y and y be the alleles of the gene responsible for seed color and R and r be the alleles of the gene responsible for seed shape. Capital letter is for dominant allele and small letter is for recessive allele.

Being dominant traits, both the parents should have at least one dominant allele of both the genes. It is because the phenotype of both parents is yellow and round seeds.

In addition, F1 shows single phenotype for seed color but both phenotype for seed shape. The presence of recessive phenotype in F1 indicates that both the parents must be heterozygous for seed shape, that is, Rr.

However, for seed color, it is possible that either one or both were homozygous, that is, either both YY or one parent is YY and another parent is Yy.