What is a Method of Determining the Genotype of an Individual

Question

What is a method of determining the genotype of an individual with a dominant phenotype?  
A) Monohybrid cross
B) Testcross
C) Law of segregation
D) Genetic analysis
E) Genetic fingerprinting

Accepted Answer

A testcross involves crossing an individual with a dominant phenotype with a homozygous recessive individual. If the individual with the dominant phenotype is homozygous, then all offspring will have the dominant phenotype. However, if the individual is heterozygous, then the offspring will have a 1:1 ratio of dominant and recessive phenotypes. This can help determine the genotype of the individual with the dominant phenotype.