Allele

An allele is a form of a gene at a particular position (locus) on a chromosome.^[1]15 It is the bit of coding DNA at that place.^[2]p6

Typical plants and animals have two sets of chromosomes, one set inherited from each parent.^[1]123 These organisms are called diploid. Since such organisms have two sets of chromosomes, they have (except on the sex chromosomes) two alleles at each gene locus.^[2]p6

If the two alleles are identical, the individual is called a homozygote and is said to be homozygous. If instead the two alleles are different, the individual is a heterozygote and is heterozygous.^[1]205

1. ↑ ^{1.0 1.1 1.2} King R.C. Stansfield W.D. & Mulligan P.K. 2006. A dictionary of genetics, 7th ed. Oxford.
2. ↑ ^{2.0 2.1} Gillespie, John H. 2004. Population genetics: a concise guide, 2nd ed. Johns Hopkins University Press, Baltimore.