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.
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Codominance means that neither allele can mask the expression of the other allele. An example in humans would be the ABO blood group, where alleles A and alleles B are both expressed. So if an individual inherits allele A from their mother and allele B from their father, they have blood type AB.
Suzanne Hart, Ph.D.
Associate Investigator, Medical Genetics Branch; Deputy Director, Medical Genetics Residency and Fellowship Training Programs
An American Board of Medical Genetics-certified clinical biochemical geneticist and medical geneticist, Dr. Hart uses molecular and biochemical techniques to understand genetic diseases of teeth, the oral cavity and the kidney. Gingival tissue plays a role in tooth development. Gum health contributes to overall well-being, appearance and the ability to eat and speak properly. Overgrowth of the gums can occur as an isolated inherited condition, part of a genetic syndrome, or as a side effect of medications. Dr. Hart and colleagues discovered the only known gene mutation involved in hereditary gingival fibromatosis, a rare form of gum overgrowth.