Coefficient of inbreeding

A measure of how close two people are genetically to each another. The coefficient of inbreeding, symbolized by the letter F, is the probability that a person with two identical genes received both genes from one ancestor. Take a first-cousin mating. First cousins share a set of grandparents. For any particular gene in the male, the chance that his female first cousin inherited the same gene from the same source is 1/8. Further, for any gene the man passes to his child, the chance is 1/8 that the woman has the same gene and ˝ that she transmits that gene to the child so 1/8 X ˝ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16. The added risks for the offspring of first cousins depend not only upon the coefficient of inbreeding but also upon the genetic family history and test results. For example, first cousins of Italian descent are at increased risk of carrying a gene for beta thalassemia and genetic laboratory tests may confirm that they are both beta-thalassemia gene carriers. There are always added risks in the mating of closely related persons and those risks are not entirely negligible.

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coefficient of inbreeding n a measure of the degree of inbreeding in a population expressed as the expected proportion of homozygous loci in an individual at which both alleles can be traced back to the same ancestor called also inbreeding coefficient

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(F) an expression of the probability that an individual has received both alleles of a pair from a single ancestor common to both parents, or of the proportion of loci at which he or she is homozygous. The inbreeding coefficient of an individual is the same as the coefficient of consanguinity of his or her parents. Called also Wright inbreeding c.