[Chromosome abnormalities of human gametes]

Human newborns carrying chromosomal abnormalities are the survivors of a considerably larger cohort of affected conceptions. A direct cytogenetic study of these conceptuses would imply their destruction. Moreover, the ability to determine the parental origin of an additional or missing chromosome is limited from a methodological point of view. The cytogenetic study of human gametes provides information on these mechanisms. Several large-scale studies on sperm complements of normal men give an estimated abnormality rate of 10%. Our results concerning four carriers of reciprocal translocations show no evidence for a selection against abnormal sperm. Since about 30% of the recovered eggs fail to become fertilized in IVF programs, human oocytes have become available for large cytogenetic studies. Analysis of oocytes II provides information on the first meiotic non-disjunction rate. In our sample of 405 karyotypes, the rate of aneuploidy was 27%. No relationship was established between this frequency and the mode of stimulation of ovulation. No increase was observed with maternal aging.