Inbreeding Coefficient:This term refers to the genetic similarity between two individuals. Represented by the letter F, the inbreeding coefficient indicates the likelihood that a person possesses two identical genes inherited from a single ancestor.Consider a marriage between first cousins, who share the same set of grandparents. For any gene present in the male, there is a 1/8 chance that his female cousin has inherited the identical gene from the same ancestor. Moreover, for any gene the male passes to his offspring, there is a 1/8 probability that the female also possesses that gene, and a further chance she will pass it on to their child, making the overall probability 1/8 x 1/8 = 1/16. Consequently, the inbreeding coefficient for a first-cousin marriage is F = 1/16.The potential genetic risks for children born to first cousins depend not just on the inbreeding coefficient, but also on the family’s genetic history and test results. For instance, first cousins of Italian heritage may have a higher likelihood of carrying the gene for beta thalassemia, and genetic testing might reveal that both are carriers of this gene.The genetic risks associated with close-relative unions are significant and should not be underestimated.
