The C-group pachytene bivalent with a locus characteristic for parachromosomally situated particulate bodies (parameres): a provisional map in human males.

During prophase stages of the first meiotic division in human males, an autosomal divalent in the C group (autosomes 6-12) characteristically has associated with it, at a specific locus, small, DNA-containing bodies (parameres). A pachytene chromomere map is presented, as is evidence suggesting that the parameres are disposed in two lateral loops, each of which is coaxial with one of the homologs. Stereophotographs of stacks of plates from electron micrographs of serial ultrathin sections show the parameres in their in situ configuration to be composed of tightly compacted fibrils, 85-90 A in diameter.