A Testcross Includes

Question

A testcross includes:
A)one parent who is homozygous recessive for one gene pair and a second parent who is homozygous recessive for a second gene pair.
B)one parent who is homozygous dominant for one or more genes and a second parent who is homozygous recessive for these same genes.
C)two parents who are both heterozygous for two or more genes.
D)one parent who shows the dominant phenotype for one or more genes and a second parent who is homozygous recessive for these genes.
E)one parent who shows the recessive phenotype for one or more genes and a second parent who is homozygous dominant for these genes.

Accepted Answer

A testcross involves crossing an individual with an unknown genotype to an individual with a homozygous recessive genotype. This allows for determination of the unknown genotype based on the offspring's phenotypes. In choice D, one parent shows the dominant phenotype and the second parent is homozygous recessive, which is the correct setup for a testcross.