<< Back to glossary index


Alternate forms of a gene at the same locus (position on a chromosome).

Use in clinical context

Most human cells contain pairs of homologous chromosomes; therefore, most cells will have two copies of every gene. At any particular locus, the two genes may be identical (same allele) or different (different alleles). For each gene, every variant in that sequence generates a new allele.

Some, but not all, alleles have functional implications. For example, the BRCA1 gene has more than 1,000 different pathogenic variants, and therefore over 1,000 disease-associated alleles.

Related terms

Chromosome | Codon | Gene | Locus

Last updated on 21st October, 2020