AP BIOLOGY

Detailed explanation-1: -A test cross is a cross between heterozygous F1 generation and recessive parent. That is, Ww (F1 generation) x ww (recessive parent)

Detailed explanation-2: -A cross between two organisms, one of which has an unknown genotype and the other with a homozygous recessive trait is called a test cross.

Detailed explanation-3: -The individual in question is crossed to a tester (homozygous for the recessive allele-genotypically aa). A cross of AA X aa would produce progeny that are all Aa genotypically and all progeny would express the dominant phenotype.

Detailed explanation-4: -Testcross is a cross of any genotype showing dominant phenotype with a recessive homozygote to determine the genotype of a dominant parent if it is a heterozygous-or homozygous-dominant. Being a hybrid Tt shows dominant phenotype and tt is the recessive parent; it is a test cross. Option A is correct.