Question

if several pea plants with genotype yy are crossed with pea plants with the genotype yy, what percentage of the offspring will be expected to have the yy allele combination?

40%

75%

50%

25%

Explanation:

Step1: Set up Punnett square

The parent genotypes are Yy (produces Y and y gametes) and yy (produces y and y gametes). The Punnett square is:

	Y	y
y	Yy	yy

Step2: Calculate ratio of yy

Out of 4 possible offspring genotypes (Yy, yy, Yy, yy), 2 are yy. So the proportion is $\frac{2}{4} = 0.5$ or 50%.

Answer:

50% (corresponding to the option "50%")