Tay-Sachs disease and the persistence of lethal autosomal recessive genes in human populations.

Several lethal autosomal recessive genes have stable carrier frequencies of about 1:20-30 in certain communities, while being exceedingly rare in other, biologically equally successful communities sharing the same environment. It is shown that this situation could persist indefinitely, without invoking the concepts of heterozygote advantage or epistasis, if the parents of affected offspring replace such children with additional sibs. We believe that this could be an important biological mechanism which ensures the maintenance of genetic diversity in the face of natural selection.