AN ESTIMATE OF THE MUTATIONAL DAMAGE IN MAN FROM DATA ON CONSANGUINEOUS MARRIAGES

Abstract

From studies of the increased mortality in children of consanguineous marriages it is estimated that the average person carries heterozygously the equivalent of 3-5 recessive lethals acting between late fetal and early adult stages. Assuming that the most important effect of detrimental "recessive" mutations in populations that undergo little present inbreeding is through heterozygous damage, and using Drosophila data to estimate the amount of this, the frequency of deaths in the populations studied due to the same factors as those causing the additional deaths in consanguineous marriages is estimated as 6-10%. From this we estimate a total mutation rate of .03-.05 per gamete per generation to such genes. Since the total, in- cluding those causing early undetected embryonic deaths and detrimental effects after maturity, is probably 2-3 times as high as that accounted for here, the total mutation rate to lethals and detrimentals is estimated as .06-. 15 gamete per generation or, with 104 loci per gamete, 6-15 x 10-6 per locus.