A testcross of an organism of unknown genotype is done when the organism is crossed with an organism that is:
A)a heterozygote.
B)a dominant homozygote.
C)a recessive homozygote.
D)All of these choices are correct.

Question

Quizplus · Accepted Answer

A testcross is done to determine the genotype of an organism, typically one that displays a dominant phenotype. The organism is crossed with a homozygous recessive organism to determine whether the unknown organism is heterozygous or homozygous dominant. Therefore, the correct choice is C, a recessive homozygote. Choices A and B are incorrect because a heterozygote or dominant homozygote would not provide information on the unknown organism's genotype.

A Testcross of an Organism of Unknown Genotype Is Done