Lampbrush chromosomes from growing oocytes of the Japanese quail (Coturnix coturnix japonica) were studied by phase contrast, light and electron microscope techniques. At diplotene, there are 38 macro- and microbivalents and two unpaired sex heterochromosomes. in each nucleus. During previtellogenesis all of them are in the state of lampbrushes with well developed lateral loops. The lengths of chromosomes and their lateral loops change depending on the oocyte diameter. The longest lampbrushes with maximal lateral loops can be observed within the oocytes of 0.5-0.75 mm in diameter. The lengths of lateral loops vary from one to fifty microns; the avarage contour lenghth of the loop being about 15 mkm. According to the classification of lateral loop types by Callan (1963), all the loops in the quail lampbrush chromosomes belong to the normal ones. They demonstrate certain asymmetry and, as a rule, contain a few linear units of RNP matrix with a visible polarity. During viellogenesis chromosomes become shorter, lateral loops also become smaller and less numerous, neighbour chromomeres fuse. Taking into account the relative lengths of chromosomes, the distribution of chiasmata, the sizes and distribution of lateral loops and chromomeres, we were able to identify and describe three biggest bivalents, certain microbivalents and the univalent Z chromosome. No nucleoli were present in the nuclei of oocytes in adult females.
The authors were wrong describing ZW bivalent as a Z univalent chromosome. Later, the ZW bivalents in lampbrush phase were identified and described in different birds by the same authors (Khutinaeva et al., 1989; Chelysheva et al., 1990; Solovei et al., 1990, 1993).