Cytological studies of meiotic recombination in human males.

We combined immunostaining and fluorescence in situ hybridization (FISH) methodology to directly examine meiotic exchanges in over 2,000 pachytene stage spermatocytes from 25 individuals. Our results indicate that, on average, there are about 50 exchanges per cell and that, with the exception of the acrocentric chromosomes, all chromosome arms harbor at least one exchange. We also identified significant among-individual variation in the mean number of exchanges, with an approximate 20% difference between individuals with "low" and those with "high" exchange frequencies. Copyright 2004 S. Karger AG, Basel.