Cytogenetic analysis of first cleavage fertilized mouse eggs following in vivo exposure to ethanol shortly before and at the time of conception.

In this study, the chromosome constitution of mouse eggs exposed in vivo to a dilute solution of ethanol during specific stages of the first and second meiotic divisions was determined at the first cleavage mitosis. Exposure to ethanol prior to the completion of the second meiotic division induced an incidence (7-10%) of aneuploidy involving only one chromosome in 98% of malsegregation events. This investigation provides indirect evidence that ethanol may induce aneuploidy by disrupting the functioning of the meiotic spindle. Karyological analyses of chromosome spreads prepared at the first cleavage metaphase suggest that only a small proportion of the total chromosome complement may be induced to undergo malsegregation.