<Table> <Tr> <Td> </Td> <Td> This article relies largely or entirely on a single source . Relevant discussion may be found on the talk page . Please help improve this article by introducing citations to additional sources . (April 2009) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article relies largely or entirely on a single source . Relevant discussion may be found on the talk page . Please help improve this article by introducing citations to additional sources . (April 2009) </Td> </Tr> <P> In genetics, a test cross, first introduced by Gregor Mendel, involves the breeding of an individual with a phenotypically recessive individual, in order to determine the zygosity of the former by analyzing proportions of offspring phenotypes . Zygosity can either be heterozygous or homozygous . Those that are heterozygous have one dominant and one recessive allele . Individuals that are homozygous dominant have two dominant alleles, and those that are homozygous recessive have two recessive alleles . </P> <P> The genotype that an offspring has for each of its genes is determined by the alleles inherited from its parents . The combination of alleles is a result of the maternal and paternal chromosomes contributed from each gamete at fertilization of that offspring . During meiosis in gametes, homologous chromosomes experience genetic recombination and segregate randomly into haploid daughter cells, each with a unique combination of maternally and paternally coded genes . Dominant alleles will override the expression of recessive alleles . </P>

What is a test cross and what is its purpose
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