Homozygoten

Homozygoten, or homozygotes, are individuals that carry two identical alleles for a given gene at a specific locus on paired chromosomes. In diploid organisms, a locus can be homozygous (for example AA or aa) or heterozygous (Aa). The phenotype of a homozygote follows the allele it carries: a homozygous dominant (AA) typically expresses the dominant trait, and a homozygous recessive (aa) expresses the recessive trait. Heterozygotes (Aa) carry one copy of each allele and may display the dominant phenotype or show other patterns of inheritance depending on dominance, codominance, or incomplete dominance.

In population genetics, homozygosity is influenced by mating patterns and population size. Inbreeding and small populations increase the proportion of homozygous loci, reducing genetic diversity. Researchers quantify this with measures such as observed homozygosity and expected homozygosity, and with the inbreeding coefficient F = (He − Ho)/He. Modern genomic methods detect runs of homozygosity, contiguous stretches of homozygous genotypes, which indicate recent common ancestry or autozygosity.

Homozygoten is the plural form in German for homozygotes, used in multilingual genetics literature. In English, the plural is homozygotes. The study of homozygosity is important for understanding trait expression, recessive diseases, and the genetic consequences of inbreeding and demographic history.