Test Cross
The purpose of a test cross is to determine the unknown genotype of an individual exhibiting a dominant phenotype.
The unknown individual is crossed with an individual the has the recessive phenotype so that any recessive alleles present in the unknown will be expressed in the phenotypes of the offspring since the recessive parent contributes only recessive alleles.
Results of a Test Cross:
­ If all of the offspring show the dominant trait, the unknown genotype is most likely homozygous dominant.
­ If any of the offspring show the recessive trait, the unknown genotype is heterozygous.
Test Cross
Testcross = homozygous recessive X unknown genotype A testcross is performed when you need to determine the genotype of an individual that shows the dominant trait. Their genotype may be either ...
(a) homozygous dominant or
(b) heterozygous
1