Inbreeding coefficient The probability of homozygosity by descent (having common ancestors). The probability that a zygote obtains copies of the same ancestral gene from both its parents because they are related. The probability of autozygosity.
The value ranges from 0 in a large random-mating population, to 1.0 when complete homozygosity at all loci is attained.
Coined by Wright, 1929.