Glossary

Genetic diversity

The variety of genes within a breed or population; closed stud books and heavy use of a few popular sires reduce it and make inherited conditions more common.

Also called: gene pool, genetic bottleneck, popular sire effect, founder effect, breed diversity, closed stud book

Genetic diversity is the amount of variation in the genes of a group of dogs. A breed with high diversity has many unrelated lines. Most registries run a closed stud book, which means only dogs whose parents are registered can be added, so the gene pool is fixed once the breed is established. Over time it shrinks when a few popular sires father many litters or when a population drops sharply, and that is called a bottleneck.

Less diversity makes it likelier that harmful gene variants pair up, and inherited conditions become more common in some breeds. Breed clubs respond with health databases, inbreeding coefficient tools, and some have allowed outcrossing, as with the Dalmatian backcross for a urinary trait.

A landrace dog population usually keeps a wide mix of genes.

Last reviewed November 8, 2026

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Related terms

Inbreeding coefficient A percentage showing how likely a dog is to carry two identical copies of a gene from a shared ancestor, a measure of how closely related its parents were. Landrace dog A local population of dogs shaped by climate, work and natural selection in one region, rather than by a written breed standard and closed stud book. Purebred A dog whose parents and ancestors belong to one recognised breed and are recorded in a registry, so its ancestry can be traced on paper. Foundation Stock Service An AKC record-keeping program for rare breeds not yet fully recognised, letting breeders register dogs on the way to full recognition.