Figure 2.

Inheritance of sperm chromatin structural elements by the embryo. DNA in round spermatids is packaged by histones (top) but during spermiogenesis, most of these are replaced by protamines (middle, red). After fertilization, the protamines are removed, and histones supplied by the oocyte replace them (bottom, light green). However, some histones that were retained in the spermatozoon (middle, dark green) are probably retained in the newly formed paternal pronucleus after fertilization. Sperm nuclear matrix attachment regions (MARs) are probably retained in the paternal pronucleus as well.