- Situation in which two different alleles for a genetic trait are both expressed.
Definition from: Human Genome Project Information
at the U.S. Department of Energy
- Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked. In codominance, however, neither allele is recessive and the phenotypes of both alleles are expressed.
Definition from: Talking Glossary of Genetic Terms from the National Human Genome Research Institute
Related discussion in the Handbook
See also Understanding Medical Terminology.