How do you setup a Test Cross? How do you use it to identify an unknown partent?

Answer 1

A test cross is used to determine the genotype of an unknown individual with a dominant phenotype. This is done by crossing with a homozygous recessive individual.

If the unknown individual is homozygous dominant all the offspring will show the dominant phenotype.

If the unknown individual is heterozygous 1/2 the offspring will show the dominant phenotype, and the other 1/2 will show the recessive phenotype.