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the state of the genetic apparatus of an organism in which homologous chromosomes have the identical form of a given gene. The transition of a gene into the homozygous state leads to the manifestation in the organism’s structure and function (phenotype) of recessive alleles, whose effect in heterozygosis is suppressed by the dominant alleles. A test for homozygosis is the absence of splitting in certain forms of crossbreeding. A homozygous organism produces only one form of gamete for a given gene.