Allelic Variants

Origin

The term combines the Greek root allelon, meaning “of one another” or “reciprocal,” referring to the paired nature of genes on chromosomes, with variant, from the Latin varians, meaning “changing.” The concept originated with Gregor Mendel’s laws of inheritance, which described the existence of alternative factors, later identified as alleles, that determine distinct traits. The term is foundational to modern genetics and pharmacogenomics, especially when analyzing individual biological responses.

Mechanism

The presence of a specific allelic variant modulates the transcription or translation efficiency of the corresponding gene, ultimately affecting the structure or quantity of the resulting protein. For instance, a variant might produce a less active metabolizing enzyme, causing a drug or hormone metabolite to accumulate, or it might create a receptor with reduced binding affinity. This subtle molecular change translates into observable physiological differences, influencing an individual’s susceptibility to disease or their unique response to exogenous hormonal therapy.