Methods
DNA methylation at intergenic loci along chromosomes 9 and X was examined by quantitative analysis of DNA methylation by real-time polymerase chain reaction at the time of initial acquisition of epigenetic patterns in the prenatal male germline (16.5 dpc) and compared with patterns in early post-natal spermatogonia (Day 6) and in spermatozoa in mice. DNA methylation status at CpG-rich sites across the genome was assessed in spermatogonial precursors from Day 4 male mice using restriction landmark genomic scanning. Main