Genetic linkage

Definition

The non-random co-inheritance of alleles at different loci due to their physical proximity on the same chromosome, resulting in reduced recombination frequency between them during meiosis. The strength of linkage is inversely proportional to the distance separating loci: closely spaced genes tend to be transmitted together as a unit, while distant loci or those on different chromosomes assort independently.

Etymology

From Greek genetikos (origin, generation) + Middle English link (connecting element)

Example

In the mosquito Anopheles gambiae, genetic linkage between a sodium channel mutation conferring insecticide resistance and nearby microsatellite markers allows researchers to track the spread of resistance through field populations without sequencing individual specimens.

Synonyms

• linkage
• chromosomal linkage

Related Terms

• Recombination
• Crossing over
• locus
• Allele
• chromatid
• linkage disequilibrium
• genetic map
• quantitative trait locus

Usage Notes

Linkage describes the physical relationship between loci, whereas linkage disequilibrium describes the statistical non-random association of alleles in a population, which may persist even without physical linkage due to selection or drift. Recombination frequency is measured in centimorgans (cM), where 1 cM ≈ 1% recombination. Perfect linkage (0% recombination) is rare; even adjacent genes may separate during meiosis, and interference can alter expected recombination patterns.