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  • Current: Sep 24, 2020


An allele refers to one of the alternative forms of a gene.

Typical diploid cells have two same loci on homologous chromosomes. Two allels , one from each parent, occupy the loci.

Public comain image showing alleles and loci

Definitions in the literature

  • One of two or more alternative forms of a gene [1].
  • One of the alternative forms of a gene or any other particular site (locus) on a chromosome. In a diploid cell there are usually two alleles of any one gene (one from each parent), which occupy the same locus on homologous chromosomes [2].
  • One of several alternative forms of a particular gene [3].
  • A particular version of a gene. Different alleles of the same gene often have different effects [4].