kodominie

Kodominie, in genetics, is an inheritance pattern in which both alleles of a gene in a heterozygous individual are expressed, and both phenotypic effects are observed simultaneously. In codominant relationships, neither allele is recessive, and the resulting phenotype reflects the presence of both distinct alleles.

A classic example is the ABO blood group system in humans. The IA and IB alleles are codominant; individuals with genotype IAIB express both A and B antigens on their red blood cells, producing the AB blood type. The i allele is recessive to both IA and IB, so individuals with IAi or IBi phenotypes express only A or B antigens, respectively, while ii individuals lack both antigens. Another well-known example is the MN blood group, where M and N antigens on red blood cells are determined by codominant alleles.

Codominance can also be observed in traits such as certain coat colors in animals (for example, roan horses or cattle, where red- and white-sport alleles are both expressed) and in some plant traits where two alleles produce distinct phenotypic effects. In many codominant systems, the heterozygote displays a phenotype that is clearly different from either homozygote, reflecting the simultaneous expression of both alleles. It is distinct from incomplete dominance, where the heterozygote shows an intermediate phenotype between the two homozygotes.

The molecular basis often involves the production of functional products from both alleles, such as different enzymes or structural proteins, contributing to the observed phenotype.