Final answer:
A test cross is a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual. It helps determine whether the dominant expressing individual is a heterozygote or a homozygote for the dominant trait.
Step-by-step explanation:
A test cross is a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual. This type of cross can help determine whether the dominant expressing individual is a heterozygote or a homozygote for the dominant trait. The offspring phenotypes of the test cross can provide information about the genotype of the unknown parent.