# Inbreeding Coefficient

Reference work entry

First Online:

**DOI:**https://doi.org/10.1007/978-1-4020-6754-9_8397

Denotes the probability that *two alleles at a locus in an individual* are identical by *descent* from a common ancestor, i.e., the chance that an individual is homozygous for an ancestral allele by inheritance (not by mutation). The inbreeding coefficient for second cousins is 1/64 and for third cousins it is 1/256. In case only one of the parents is common at the starting generation the inbreeding coefficient of half-sibs at uncle-niece or aunt-nephew marriage is 1/16, for first cousins 1/32, for second cousins 1/128, and for third cousins 1/512.

*Consanguinity*(coancestry) is a similar concept but the coefficient of coancestry indicates the chances that

*one allele in two individuals*would be identical by descent. F symbolizes the coefficient of inbreeding. The calculation of F is based on the fact that in a diploid at each locus there are two alleles and only one is contained in any gamete (either one in a particular egg or sperm). Thus, each individual has 0.5 chance for passing on a...

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© Springer Science+Business Media 2008