ABSTRACT
Consanguineous marriages are marriages between relatives. The coefficient of consanguinity is the probability that two relatives will both have alleles which are identical by descent from a specific allele in a common ancestor. The use of this is that their consanguinity equals the inbreeding coefficient of their offspring, but it only works for a specific allele. This is medically useful if an identified common ancestor (say a grandparent) is known to have carried a particular recessive deleterious allele. It then predicts the chance of descendants (e.g. grandchildren, who are cousins) producing children who will be affected by the genetic disorder because they are homozygous for that allele.
