Inbreeding

Inbreeding is the mating of closely related individuals, leading to increased genetic similarity between parents and offspring. In biology, it is evaluated relative to random mating in a population and tends to increase homozygosity across the genome, making recessive alleles more likely to be expressed.

The extent of inbreeding is commonly summarized by an inbreeding coefficient (F), which ranges from 0 (no relatedness) to 1 (offspring homozygous at all loci due to identical alleles from a common ancestor). Pedigree data or genomic analyses can estimate F.

Inbreeding is more common in small or isolated populations, captive breeding programs, and communities with strong cultural endogamy. It can occur unintentionally through limited mate choice or intentionally in line breeding to fix desired traits.

A major consequence is inbreeding depression, a decline in fitness arising from increased expression of deleterious recessive alleles. Effects can include reduced fertility, higher infant mortality, congenital defects, poorer immune response, and lower overall vigor, though outcomes vary by species and context.

Measurement of inbreeding uses pedigrees, Wright's inbreeding coefficient, and genomic methods such as runs of homozygosity. These tools help assess risk in conservation, livestock, horticulture, and medical genetics.

Management strategies emphasize maintaining genetic diversity by avoiding close inbreeding, introducing unrelated individuals, and managing population size. In human populations, genetic counseling and awareness of consanguinity are often recommended. In conservation biology, genetic rescue and careful breeding plans address inbreeding while balancing other goals.