Selection against chromosomally abnormal sperm?Fact or fiction?

Abstract

Martin-DeLeon and Boice (1982) recently published results from a very interesting study that appears to implicate sperm selection in mice after aging in the male genital tract. In their discussion Martin-DeLeon and Boice cited a number of papers which they construed as support for the idea of prezygotic selection against chromosomally abnormal sperm. They stated that "Rudak et al. (1978) estimated that paternal nondisjunction in man is the order of 40%" and that "Hulten and Pearson (1971) reported that sperm with multiple Y chromosomes occur much more commonly in man than the XYY karyotype is encountered in complete population surveys." Both of these studies are based on indirect evidence, assuming that the fluorescent spot(s) seen in sperm heads always reflect the presence of a Y chromosome(s). In fact, Rudak et al. did not make any estimates of paternal nondisjunction. Their paper was the first report on direct analysis of human sperm chromosomes by fertilization of hamster eggs. Rudak et al. studied one normal male and found a 5% (3/60) frequency of aneuploidy. I assume that MartinDe Leon and Boice are referring to the fluorescent Y body studies of Pawlowitzki and Pearson (1972) cited by Rudak et al. Pawlowitzki and Pearson found that 1.3% of sperm had two fluorescent spots and presumed that these sperm were 24,YY. They extrapolated this frequency of nondisjunction to other chromosomes, and this provided the estimate of nondisjunction approaching 40%. Martin-DeLeon and Boice suggested that since the frequency of aneuploidy is much lower in newborns, "chromosomally unbalanced sperm are less likely to effect