[The characteristics of the morphofunctional organization of the lampbrush chromosomes from the oocytes of the rock dove].

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.