Figure 1.

The origin of genetic and epigenetic abnormalities during spermatogenesis. The DNA methylation pattern is established during germ cell development. Spermatocytogenesis can also give rise to chromosome nondisjunction during its meiosis I and II along with double strand breaks, abnormal histone modification and alteration in the expression of mRNA and other non-coding RNAs. Abnormal protamine replacement or centrosome formation can take place at the final stage of spermatogenesis where round spermatids differentiate to mature spermatozoa. DNA fragmentation is mainly the result of apoptosis following double strand breaks or abnormal protamination during spermiogenesis.