Alleles

Part of speech: noun

Definitions

1. Variants of genes that occur at the same chromosomal location and can influence phenotypic traits in a population
2. Different forms of genetic sequences present at the same locus on homologous chromosomes that can result in variations in organisms' traits
3. Alternative genetic variants found at the same position on paired chromosomes that contribute to differences in inherited characteristics

Etymology: "Alleles" is simply the plural of "allele," so the story belongs to the singular. The word was built in German in the early twentieth century from a shortened form of "allelomorph," an English term for one of two or more forms of a gene that occupy the same position on paired chromosomes. Its deepest root is the Ancient Greek "allēlōn," meaning "each other," which itself comes from "allos," meaning "other." The Greek roots carry a sense of reciprocity: two things standing in relation to one another, each the other's alternative. The English "allelomorph" combines that Greek material with "morph," meaning "form," so the full term literally names an "other form." German geneticists then clipped it to "Allel," and English speakers borrowed the shorter German version back. The clipped form kept the original idea of alternatives standing side by side, now applied to the alternative versions of a gene that a pair of chromosomes can carry.

Synonyms: gene variants, gene types, genetic variants, genetic types, loci