Condensation of chromosomes during mitotic prophase

Abstract

Condensation of chromosomes during meiotic prophase was studied in the spermatogenesis of Omocestus sp. grasshoppers by using whole mount electron microscopy. The synaptonemal complexes may be clearly observed in the zygotene and early pachytene stages. The lateral elements of the synaptonemal complex consist of a double longitudinal axis with knotlike structures at the site of attachment of the transversal fibrils of the central region and the chromatin loops. During the pachytene stage — obviously due to accumulation of a large amount of fibrillar material onto paired homologues — the linear structure of the chromosomes is noticeably thickened by the increase of connective fibrils between the chromomeres. Supposedly, in this phase certain connections between the paired homologues may be strengthened to become cytological chiasmata. Beginning in late pachytene remnants of the nuclear envelope with numerous nuclear pore complexes were found to be attached into the chromosomes. © 1972 Mendelian Society of Lund