Question

In pea plants, the allele for purple flower color is dominant to the allele for white flower color. If you were to perform a test-cross to determine the genotype of a purple-flowered plant, you would expect the percentage of purple-flowered progeny to be _________ if the plant is homozygous and _____________ if the plant is heterozygous.

Answer 1

Answer:

100%, 50%

Explanation:

A testcross involves crossing an organism of unknown zygosity with its homozygous recessive version.

Assuming the purple flower pea plant is homozygous for the trait with genotype PP and it is crossed with homozygous recessive pea plant pp.

PP   x   pp = Pp, Pp, Pp, and Pp

100% of the progeny will be purple in appearance.

On the other hand, assuming the purple flower pea plant is heterozygous with genotype Pp and this is testcrossed with a pp plant.

Pp   x   pp = Pp, Pp, pp, and pp

50% of the progeny will be purple and the remaining 50% will be white.

Hence, If you were to perform a test-cross to determine the genotype of a purple-flowered plant, you would expect the percentage of purple-flowered progeny to be 100% if the plant is homozygous and 50% if the plant is heterozygous.