See also: outbreeding

Inbreeding is the production of offspring by genetically related parents, such as siblings.

Inbreeding increases the risk of the offspring carrying deleterious recessive traits, because it increases the probability of homozygosity in the offspring. This leads to reduced fitness of the organism and, if a regular occurrence, reduced fitness of the population as a whole in a phenomenon called inbreeding depression. In animal or crop farming where this occurs, offspring that are the result of inbreeding, and pose a risk to the overall gene pool, are often culled in a process called genetic purging.