allelic

Allelic is an adjective used in genetics to describe anything related to alleles—the alternative forms of a gene occupying the same locus. An allele is a variant form of a gene that can influence a trait or phenotype.

An individual typically carries two alleles at each autosomal locus, one inherited from each parent. When the two alleles are identical, the organism is homozygous for that locus; when they are different, it is heterozygous. Allelic variation among loci and individuals underpins much of genetic diversity in populations.

Allele frequency refers to the proportion of a population that carries a given allele and is a fundamental measure in population genetics. Studying allele frequencies helps researchers understand population structure, evolutionary processes, and disease risk across groups.

Allelic heterogeneity describes different mutations within the same gene that can produce similar or overlapping phenotypes, while different genes can also contribute to related traits. This concept helps explain why the same disease can arise from multiple genetic causes.

Allelic imbalance, or allele-specific expression, occurs when the two alleles present in a heterozygote are expressed at unequal levels, shaping the overall phenotype.

Allelic exclusion is a mechanism in the immune system that ensures only one allele of certain receptor genes is productively expressed in a given cell, contributing to receptor specificity and diversity.

In research and medicine, the concept of allelic variation informs studies of inheritance patterns, disease loci, and the interpretation of genetic tests, as well as strategies for diagnosis and therapy.