Question

. In pea plants, yellow peas (Y) are dominant over green peas (y). Use a Punnett square to predict the phenotypic and genotypic outcome (offspring) of a cross between a plant heterozygous/hybrid for yellow (Yy) peas and a plant homozygous/purebred for green (yy) peas. Step 1 | KNOW YOUR PHENOTYPE Step 2 | CHOOSE YOUR LETTERS Y=yellow Y=green Step 3 | WHO ARE THE PARENT’S? Parent 1 Parent 2

Answer 1

The genotypic outcome of the cross is while the phenotypic outcome is:

• Genotypic ratio: 1:1, YY:Yy
• Phenotypic ratio: 100% yellow

The cross involves a heterozygous yellow pea plant with genotype Yy and a homozygous/purebred pea plant with genotype YY. Both genotypes can be broken down to their gametes and arranged in a 2 x 2 Punnet's square as follows:

Y y

Y YY Yy

Y YY Yy

From the cross, the genotype ratio of the offspring is 50/50 YY/Yy while the phenotype ratio is 100% yellow offspring.

In other words:

Genotypic ratio: 1:1, YY:Yy

Phenotypic ratio: 100% yellow