Dictionary > Overdominance

Overdominance

Definition
noun
(genetics) A type of dominance characterized by a phenotype that is more pronounced in a heterozygote relative to that of the counterpart homozygote
Supplement
In genetics, dominance refers to a property of a gene (or allele) in relation to other genes or alleles wherein a gene (or allele) shows dominance as it suppresses the expression, or dominates the effects, of the recessive gene (or allele). According to the law of dominance proposed by Gregor Mendel, in a pair of genes or alleles in heterozygous condition, the allele that is expressed is described as dominant. In contrast, the allele that is not expressed is recessive. However, there are instances wherein the pattern of phenotypes does not follow the laws in inheritance proposed by Gregor Mendel. One of them is overdominance.
In overdominance, the heterozygote produced by two homozygote parents shows a phenotype that is more pronounced than that of the parents. Overdominance may also mean that the heterozygote has a higher fitness relative to the counterpart homozygotes. An example of this is a heterozygote for sickle cell anemia. The heterozygote individual would have less physiological effects of the condition and have partial resistance to malaria as opposed to the homozygotes suffering more from the deleterious effects of sickle cell anemia or have no similar protective resistance against malaria.
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Related form(s):

  • overdominant (adjective, of, relating to, or characterized by overdominance)

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