Somatic synapsis of eu- and heterochromatic regions of Drosophila melanogaster chromosomes

Abstract

Quantitative cytogenetical analysis has been used to study the synapsis of D. melanogaster neuroblast mitotic chromosomes from normal females, flies with heterozygous deletions, duplications or inversions in the heterochromatic regions of chromosome 2 and in triploid females. In all these genotypes chromocentric fusion of heterochromatic regions of heterologous chromosomes is observed. Eu-and heterochromatic regions of homologous chromosomes are intimately paired at the same time during the cell cycle. The structural rearrangements lead to reduced frequencies of chromocentric association as well as of homologous synapsis compared with the frequencies in the wild-type. The results obtained are discussed with respect to the general problem of the homologous interaction of chromosomes and the significance of heterochromatin for these processes.

Chromatin Diminution in <b><i>Cyclops kolensis</i></b> Lill. (Copepoda, Crustacea) as a Radical Way to Inactivate Redundant Genome in Somatic Cells

“…Chromocenters become detectable, and part of the chromocenters adjoin the nuclear membrane [Grishanin, 1995]. Thus, before CD, С. kolensis embryo cells have the typical structure of interphase nuclei while, after CD, the structure of interphase nuclei is irreversibly changed and now more resembles the structure of interphase nuclei observed in multicellular eukaryotic cells after differentiation [Chentzov and Polyakov, 1974;Bostock and Sumner, 1978;Semionov and Smirnov, 1984]. Although the somatic cells of C. kolensis after CD are still far from differentiated cells of the adult organism, the similarity with differentiated cells may reflect a correlation between the changes in the structure of interphase nuclei in early embryogenesis in C. kolensis and the transition from maternal gene regulation in early cleavage divisions to nuclear gene regulation in later stages when genes are mostly regulated by chromatin state.…”

A novel transvection phenomenon affecting the white gene of Drosophila melanogaster.

“…T HE somatic chromosomes of Drosophila and other Diptera are normally paired homologously in interphase nuclei (STEVENS 1908; METZ 19 16; SEMENOV and SMIRNOV 1984). This synapsis between homologous genes allows the possibility that pairing-dependent interactions between genes may affect their regulation (LEWIS 1954(LEWIS , 1955(LEWIS , 1985.…”