Numerical chromosome abnormalities in the spermatozoa of the fathers of children with trisomy 21 of paternal origin: generalised tendency to meiotic non-disjunction

The purpose of this study was the evaluation of aneuploidy frequencies in t he spermatozoa of two fathers (DP-4 and DP-5) who had children with Down sy ndrome (DS) of paternal origin and in whom a previous sperm analysis by flu oresence in situ hybridisation (FISH) had suggested a generalised tendency to meiotic non-disjunction. Sperm samples were simultaneously hybridised wi th FISH probes for chromosomes 4, 13 and 22. Disomy frequencies for each of the chromosomes and diploidy frequencies were compared with data obtained from nine control donors. Both DS fathers had a statistically significant i ncrease in the frequency of disomy for chromosomes 13 and 22. DP-5 also had an increased frequency of diploid spermatozoa. Our data suggest that the t wo DS fathers have a generalised susceptibility to meiotic non-disjunction and that acrocentric chromosomes seem to be more sensitive to such disturba nce in the meiotic process.