Define/Explain: Test cross.

(N/A) test cross is a genetic cross between an individual with a dominant phenotype (whose genotype is unknown) and an individual that is homozygous recessive for the trait.
This cross is performed to determine the genotype of the organism showing the dominant phenotype.
If the offspring show a $1:1$ ratio of dominant to recessive phenotypes,the parent is heterozygous.
If all offspring show the dominant phenotype,the parent is homozygous dominant.