Medical Term Definition

Allele

One of two or more alternative versions of a gene or genetic sequence found at the same genomic location.

An allele is a particular version of a gene. Because humans generally have two copies of most chromosomes, one inherited from each biological parent, many genes have two alleles in an individual’s genome, although the alleles can be the same or different.

Differences between alleles can influence traits or biological characteristics, including susceptibility to certain diseases or how a person responds to particular medicines. Not every difference between alleles produces an observable effect.

QUICK FACT
A gene is a functional unit of genetic information; an allele is a particular version of that gene.

COMMONLY CONFUSED WITH

  • Gene: a functional unit of genetic information; a gene can have different alleles.
  • Mutation: a change in a genetic sequence. A mutation can create a new allele, but the terms are not interchangeable.
  • Chromosome: a larger structure containing many genes and other DNA sequences.

SEE ALSO