Homozigóta

Homozigóta is a term used in genetics to describe an organism that carries two identical alleles at a given genetic locus. In diploid organisms, such as humans and most animals, each gene exists in two copies, one on each homologous chromosome. If the two copies are the same, the genotype is homozygosity; if they differ, the genotype is heterozygous.

Two common forms of a homozygous genotype are homozygous dominant (for example AA) and homozygous recessive (aa). The phenotype depends on the alleles and the dominance relationship: a dominant allele may produce the same phenotype in both AA and Aa, whereas a recessive phenotype typically appears only when the two copies are the recessive allele (aa).

Homozygosity has several implications. In medical genetics, recessive diseases arise when an individual is homozygous for a pathogenic recessive allele. In breeding, breeders often seek homozygous lines to ensure uniform traits; these lines can be produced by controlled inbreeding or selfing. In natural populations, the level of homozygosity reflects inbreeding and genetic structure; high homozygosity can reveal deleterious recessive alleles through inbreeding depression. Modern genomic analyses also measure runs of homozygosity to infer population history and inbreeding levels.

See also: homozygosity, heterozygote, polymorphism, inbreeding, pure line.