Recessive gene

In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype. However, the term "recessive gene" is sloppy language use. Properly, it is the phenotype (or trait) which is recessive, not the gene.

Dominance/recessiveness refers to phenotype, not genotype. An example to prove the point is sickle cell anemia. The sickle cell genotype is caused by a single base pair change in the beta-globin gene: normal=GAG (glu), sickle=GTG (val). There are several phenotypes associated with the sickle genotype:

1. anemia (a recessive trait),
2. blood cell sickling (partially dominant),
3. altered beta-globin electrophoretic mobility (codominant), and
4. resistance to malaria (dominant).

This example demonstrates that one can only refer to dominance/recessiveness with respect to individual phenotypes.

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See also

• Recessive trait
• Dominant gene
• Dominant trait
• Incomplete dominance
• Dominance relationship