Direct estimation of the non-disjunction rate at first meiotic division in the human male. Preliminary results.

Chromosomal analysis of 100 second metaphases from 19 men attending an infertility clinic for various reasons was carried out to estimate the rate of non-disjunction occurring at first meiotic division. Second metaphases were selected on the basis of the good spread of their chromosomes. Karyotypes were performed using the relative length of the chromosomes and the centromeric index. Among aneuploid cells, only those containing a hyperhaploid complement (24) were regarded as informative. Of the 100 MII cells, two were hyperhaploid. The frequency of aneuploid MII cells following non-disjunction at first meiotic division is compared to the rate of aneuploid spermatozoa observed after using fertilization of zona-free golden hamster eggs.