Practice question

Sperm DNA packaging diverges from somatic chromatin organization to ensure hydrodynamic shape and protection during transit. Histones replaced by protamines PRM1 and PRM2 small basic proteins rich in arginine and cysteine forming disulfide bonds. Protamines coil DNA into donut-shaped toroids, reducing nuclear volume tenfold, silencing transcription and conferring resistance to nucleases and oxidative stress. Correct protamine ratio critical; excess PRM1 or PRM2 leads to incomplete condensation, DNA fragmentation and infertility. Compact protamine-based chromatin safeguards paternal genome en route to oocyte and ensures epigenetic delivery, embryonic integrity and genome stability post-fertilization.