Question

when two heterozygous parents are crossed (aa x aa), what percent of the offspring will have a dominant phenotype? a 50% b 75% c 100% d 25%

Explanation:

Step1: Set up Punnett - square

The parents are both Aa. The possible gametes from each parent are A and a.

Step2: Fill in Punnett - square

	A	a
a	Aa	aa

Step3: Determine phenotypes

Genotypes AA, Aa, and Aa show the dominant phenotype. There are 3 out of 4 genotypes that show the dominant phenotype.

Step4: Calculate percentage

The percentage of offspring with the dominant phenotype is $\frac{3}{4}\times100\% = 75\%$.

Answer:

b. 75%