inbreeding /in″brēding/ [L, in, within; AS, bredan, to reproduce] , the production of offspring by the mating of closely related organisms, the most extreme form being self-fertilization, which occurs in certain plants and animals. Inbreeding increases the chance that recessive alleles for both desirable and undesirable traits will become homozygous and be expressed phenotypically. In humans the amount of inbreeding in a specific population is largely controlled by tradition and cultural practices. Inbreeding is a standard agricultural method for developing desirable genotypes and pure lines in plants and animals. Compare outbreeding.