6.3: Change in diversity: inbreeding

Inbreeding is the result of mating two related individuals. Related individuals genetically are more alike than non-related individuals because they share alleles. They share alleles because they have an ancestor in common. This common ancestor passed on the same alleles to multiple offspring, who passed them on again, so that eventually they ended up in both related animals. Mating those animals creates the chance that both of them pass the same alleles on to their offspring, resulting in homozygosity in the offspring. The level of inbreeding in an animal depends on the level of relatedness between its parents, and thus the probability that both will pass the same allele on to their offspring.

The level of inbreeding in an animal can be expressed in the inbreeding coefficient. The inbreeding coefficient indicates the probability that an individual receives the same allele from both his parents, because his parents are related. Inbreeding is the result of mating related individuals. The inbreeding coefficient takes values between 0 (0% or not inbred) and 1 (100% or fully inbred). Important to keep in mind is that inbreeding increases homozygosity (and decreases genetic diversity).