A test cross is a useful way of testing a genetic hypothesis as the phenotypic frequencies of the offspring reveal the relative genotypic frequencies of the different gametes produced by the heterozygous parent . This technique was first described my Gregor Mendel. The test cross is achieved by crossing an individual that is heterozygous for a gene with an individual that is homozygous recessive for the same gene, as the homozygous recessive parent can only pass on recessive alleles the segregation of the alleles from the heterozygote is visible within the phenotype, and therefore the genotype of the progeny can be identified. The principle of a test cross is the same whether a single gene or multiple genes are involved 
- ↑ Daniel L Hartl and Maryellen Ruvolo (2012). Genetics, analysis of genes and genomes. 8th ed. London: Jones and Bartlett Learning International. 89.
- ↑ Ilona Miko, Ph.D. (2008). Test Crosses. Available: http://www.nature.com/scitable/topicpage/test-crosses-585. Last accessed 24/11/14.