Practice question

During spermiogenesis histones are sequentially replaced first by transition proteins then by small arginine-rich protamines PRM1 and PRM2. This exchange packages DNA into highly condensed toroidal structures, reducing nuclear volume, transcriptionally silencing genome and shielding paternal chromosomes from oxidative and nucleolytic damage during transit through male and female tracts. Disulfide crosslinking between protamines stabilizes compaction giving characteristic hydrodynamic sperm head shape. Balanced PRM1 to PRM2 ratio is critical; imbalance correlates with DNA fragmentation, male infertility, poor embryo development due to faulty chromatin packaging, genome instability and epigenetic dysregulation.