Protamines substitute for histones in the chromatin of sperm during the haploid phase of spermatogenesis. They compact sperm DNA into a highly condensed, stable and inactive complex. This protamine condenses spermiogenic chromatin in a pattern which comprises fibers with a progressively larger diameter and lamellae that finally undergo definitive coalescence. Cross-linked by interchain disulfide bonds around the DNA-helix. Testis.