Path: utzoo!utgpu!watserv1!watmath!iuvax!bionet!umrvmb.bitnet!C0613 From: C0613@umrvmb.bitnet ("Ronald L. Frank") Newsgroups: bionet.molbio.genbank Subject: Re: Marriages among cousins. Message-ID: <9002031741.AA03652@net.bio.net> Date: 2 Feb 90 16:38:57 GMT References: Sender: daemon@genbank.BIO.NET Lines: 25 We all have a small percentage of mutations which interrupt a few of our genes and prevent their function. Being diploid, i.e., two copie of all genes, the second gene is usually sufficient to provide the necessary function and the defect is unnoticed throughout life. With the large number of genes we have, the likelihood that two individuals randomly chosen from a population would have a defect in the same gene is extremely rare. However, we will pass this defective gene to one-half of our children. They will be normal because they inherited their second (normal functioning) gene from our spouse. Likewise all children arrying the defective gene unnoticed will pass it to one-half their children. Cousins, therefore, have a very high (relative to the general population, about 1/16) likelihood of carrying the same gene defect. The result of the defect when it is finally manifested in the children of this consnguineous marriage can range in severity from totally undetectable to sligh t inborn errors of metabolism to retardation to severe birth defects to death, and everything in between. The defect depends on the function of the gene invo lved. Quite often the death symptom can go unnoticed also as spontaneous abort ion very early in development (before a person knows they're pregnant). Unfortunately, new and previously undescribed genetic diseases will continue to be introduced into the world as long as cousins continue to marry each other. rlf