Inzucht

Inzucht, or inbreeding, refers to mating between related individuals, resulting in increased homozygosity and a higher likelihood that offspring inherit identical copies of recessive alleles from a common ancestor. In population genetics, the degree of relatedness is quantified by measures such as the inbreeding coefficient (F). Higher F values indicate greater probability of homozygosity.

Inbreeding can occur in small, closed populations where limited mate choice exists, in animal breeding programs that aim to fix desirable traits, or in human populations with consanguineous marriages or endogamous practices. The main genetic consequence is inbreeding depression: increased risk of recessive disorders, reduced fertility and viability, developmental problems, lower litter or birth weights, and, in some cases, reduced life expectancy. The effects depend on the frequency of deleterious recessive alleles and the population's history.

Inbreeding can be accompanied by reduced genetic diversity, loss of adaptability, and accumulation of harmful mutations over time. Conversely, some short-term advantages can emerge from homozygosity of favorable alleles, but these are typically outweighed by the long-term costs.

Management strategies include avoiding mating between close relatives, promoting outbreeding or merit-based crossbreeding, maintaining larger effective population sizes, and, in humans and animal genetics, genetic counseling and screening for carriers of recessive disorders. In conservation biology, carefully planned breeding programs aim to balance trait selection with genetic diversity to minimize inbreeding depression.