What does allele mean?
An allele is one of two or more alternative forms of a gene, arising through mutation and occupying the same position, or locus, on a chromosome. Because humans inherit one copy of most genes from each parent, an individual typically carries two alleles per gene — these may be identical or different, and their interaction determines how a trait is expressed. A dominant allele masks the effect of a recessive partner, which is why some inherited characteristics skip generations. The term pervades genetics and medicine: researchers speak of wild-type, mutant, dominant, and recessive alleles when studying inheritance, disease risk, and evolution. Although strictly technical in register, 'allele' has entered general educated vocabulary thanks to popular coverage of DNA testing and ancestry. Its adjective form, 'allelic', describes phenomena involving alleles, and the older coinage 'allelomorph' survives mainly in historical texts. Understanding the word is essential to grasping modern discussions of heredity.
nounOne of two or more alternative forms of a gene that arise by mutation and are found at the same position on a chromosome; an individual inherits one allele from each parent for each gene.
- One of two or more alternative forms of a gene at the same locus on homologous chromosomes.
"Each parent contributes one allele for the blood-type gene, which together determine the child's blood group."
"The recessive allele for blue eyes is masked when a dominant brown-eye allele is present."
"Geneticists sequenced both alleles to determine whether she had inherited the mutation from her mother or her father."
Standard plural; used freely in scientific writing when referring to multiple variants within a population or individual.
"The population contains several alleles of the lactase gene."
You carry roughly two alleles for most of your genes — but for some genes, hundreds of different alleles exist across humanity.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of allele
The word derives from the Greek 'allēlōn', meaning 'of one another' or 'reciprocally'. It was introduced in the early twentieth century as an abbreviation of 'allelomorph', the term coined by William Bateson and Reginald Punnett for contrasting hereditary characters. German geneticists shortened it to 'Allel', and English adopted the form 'allele' shortly thereafter. The same Greek root underlies related terms such as allelomorph and allelism, and echoes of it appear in 'parallel'.
Related word forms
How allele is actually used
Strictly a technical term of genetics, used almost exclusively in scientific, medical, and educational contexts; it does not appear in casual conversation outside those settings. Plural is 'alleles'. The adjective 'allelic' describes traits or interactions involving alleles.
Easily confused with allele
A gene is the whole stretch of DNA coding for a trait, while an allele is one specific variant of that gene.
An alley is a narrow street or passageway, whereas an allele is a variant form of a gene; they differ markedly in meaning despite a similar look.