A measure of the probability that a gene in one individual will be identical by descent to a gene in a particular relative. An equivalent and alternative measure is the proportion on an individual's genome that is identical by descent to the relative's genome. Note that the genes must be identical by descent and not simply genes shared by the population as a whole. This means that r is the probability that a gene common to two individuals is descended from the same ancestral gene in a recent common relative.
The coefficient of genetic relatedness is important in understanding the concepts of inclusive fitness and altruism.
Subjects: Zoology and Animal Sciences.