[The characteristics of the morphofunctional organization of the lampbrush chromosomes from the oocytes of the rock dove]. / Osobennosti morfofunktsional'noi organizatsii khromosom tipa lampovykh shchetok iz ootsitov sizogo golubia.

Nuclei and chromosomes isolated from growing oocytes of the pigeon C. livia have been studied by light microscope techniques. The pigeon chromosomes in diplotene assume a lampbrush form with a well expressed chromomere-loop organization. The lampbrush chromosomes (LC) with most extended lateral loops were observed in the oocytes 0.5-1.5 mm in diameter. A mean loop contour length on the preparations from oocytes of such a diameter varied within 11-16 mkm. A comparison of the pigeon LC with those of representatives of the order Galliformes described earlier (domestic fowl and Japanese quail) revealed essential differences. The LC of the pigeon are longer than those of the domestic fowl or Japanese quail. This fact well compares with the differences in DNA contents in the genomes of these species (haploid DNA quantities in genomes of the pigeon and the fowls are 1.9 and 1.2 pg, respectively). A specific feature of the pigeon LC is an even distribution of lateral loops along the chromosomal length. The central parts of the bivalents have a chromomere-loop organization typical of LC, but no chromomeres were observed, and the lateral loops were absent in the prolonged terminal regions. These regions are likely to be transcriptionally inactive. A specific structures of different types form on the pigeon LC. There are no such structures on the LC of Galliformes. Taking into account relative lengths of the chromosomes, the number and distribution of chiasmata, the location of the marked structures, an attempt was made to identify the macrobivalents of the pigeon, including the sex Z/W-bivalent.

[Heterochromatin regions of the chromosomes of the hen and Japanese quail in mitosis and at the lampbrush stage]. / Geterokhromatinovye raiony khromosom kuritsy i iaponskogo perepela v mitoze i na stadii lampovykh shchetok.

The mitotic and lampbrush chromosomes of the domestic fowl and Japanese quail were analysed by fluorochrome staining technique. The lampbrush chromosomes of both the subjects displayed a typical "loop-chromomere" structure. Three distinct kinds of loops were distinguished in Gallus g. domesticus--normal, telomeric bows, and lumps. The former are distributed along the whole chromosome length. The latter and the bows were observed in subtelomeric and telomeric regions. By DNA/RNA specific acridine orange staining it was shown that each loop (especially, "lumpy" loops) contained a rich RNP matrix. A comparative analysis of the chromomycin A3/distamycin A banding pattern of mitotic and lampbrush chromosomes shows that the telomeric "bows" and "lumps" are special loops developed in telomeric heterochromatic bands. In Coturnix c. japonica, the CMA/DA-positive bands were not observed in telomeres of mitotic macrochromosomes, except a smallest band in the 2p-arm telomere. The absence of telomeric heterochromatic bands which can be visualized in the quail mitotic chromosomes coincides with the absence of "bow"-like loops. Only small lump-like structures were seen in some telomeres of macroautosomes. The biological significance of loop formation and RNA synthesis in heterochromatic band loops in growing oocytes is briefly discussed.