A testcross involves an individual exhibiting the dominant phenotype but an unknown genotype being crossed with an individual that has a(n) ___________ genotype.
A) homozygous dominant
B) heterozygous dominant
C) homozygous recessive
D) any of the choices

Question

Quizplus · Accepted Answer

The individual exhibiting the dominant phenotype but with an unknown genotype could either be homozygous dominant (AA) or heterozygous dominant (Aa). In a testcross, it is crossed with an individual that is homozygous recessive (aa) to determine the unknown genotype. This is because if the dominant individual is homozygous dominant, all the offspring will have the dominant phenotype (Aa), but if it is heterozygous dominant, then there will be a 1:1 ratio of dominant and recessive offspring.

A Testcross Involves an Individual Exhibiting the Dominant Phenotype but an Unknown