Any one of a series of two or more different genes that may occupy the same locus on a specific chromosome. As autosomal chromosomes are paired, each autosomal gene is represented twice in normal somatic cells. If the same allele occupies both units of the locus, the individual or cell is homozygous for this allele If the allele’s are different, the individual or cell is heterozygous for both allele’s. See: DNA markers. See Also: dominance of traits. Syn: allelomorph.

Dominant traits or conditions are caused by inheritance of a single allele from either parent; recessive ones by inheritance of a relevant allele from each parent. With the advent of DNA technology, the allele has become the focus of intense scrutiny, as molecular biologists attempt to track down genes responsible for physical and behavioral traits, and for the 3,500 human diseases that have been identified as chromosomally linked. Paired with radioisotopes or fluorescent dyes, alleles may serve as probes that allow for the identification of such genes.


codominant allele

silent allele