B Chromosomes in Grasshoppers: Different Origins and Pathways to the Modern Bs

B chromosomes (Bs) were described in most taxa of eukaryotes and in around 11.9% of studied Orthopteran species. In some grasshopper species, their evolution has led to many B chromosome morphotypes. We studied the Bs in nine species (Nocaracris tardus, Nocaracris cyanipes, Aeropus sibiricus, Chorthippus jacobsoni, Chorthippus apricarius, Bryodema gebleri, Asiotmethis heptapotamicus songoricus, Podisma sapporensis, and Eyprepocnemis plorans), analyzing their possible origin and further development. The studied Bs consisted of C-positive or C-positive and C-negative regions. Analyzing new data and considering current hypotheses, we suggest that Bs in grasshoppers could arise through different mechanisms and from different chromosomes of the main set. We gave our special attention to the Bs with C-negative regions and suggest a new hypothesis of B chromosome formation from large or medium autosomes. This hypothesis includes dissemination of repetitive sequences and development of intercalary heterochromatic blocks in euchromatic chromosome arm followed by deletion of euchromatic regions located between them. The hypothesis is based on the findings of the Eyprepocnemis plorans specimens with autosome containing numerous intercalary repeat clusters, analysis of C-positive Bs in Eyprepocnemis plorans and Podisma sapporensis containing intercalary and terminal C-negative regions, and development of heterochromatic neo-Y chromosome in some Pamphagidae grasshoppers

Origin and Evolution of the Neo-Sex Chromosomes in Pamphagidae Grasshoppers through Chromosome Fusion and Following Heteromorphization

In most phylogenetic lineages, the evolution of sex chromosomes is accompanied by their heteromorphization and degradation of one of them. The neo-sex chromosomes are useful model for studying early stages of these processes. Recently two lineages of the neo-sex chromosomes on different stages of heteromorphization was discovered in Pamphagidae family. The neo-sex chromosome heteromorphization was analyzed by generation of DNA probes derived from the neo-Xs and neo-Ys followed with chromosome painting in nineteen species of Pamphagidae family. The homologous regions of the neo-sex chromosomes were determined in closely related species with the painting procedure and image analysis with application of the Visualization of the Specific Signal in Silico software package. Results of these analyses and distribution of C-positive regions in the neo-sex chromosomes revealed details of the heteromorphization of the neo-sex chromosomes in species from both phylogenetic lineages of Pamphagidae grasshoppers. The hypothetical mechanism of the neo-Y degradation was suggested. It includes expansion of different repeats from the proximal neo-Y chromosome region by inversions, spreading them towards distal region. Amplification of these repeats leads to formation of C-positive regions and elimination of the C-negative regions located between them

THE SYSTEMS OF IDENTIFICATION OF THE HOLOGIC REGIONS OF THE CHROMOSOMES: A COMPARATIVE CYTOGENETICS OF MAMMALS AND CHROMOSOME PATHOLOGIES OF THE MAN

The new systems of the analysis of chromosomes on the high level of resolution in the cases, excluding the reception of the analogous results by other methods, have been developed. The base for mapping the genomes of the mink and fox has been created. The comparative analysis of the carnivorous animals and the man's chromosomes has been performed. The presence of the differences in the tempoes of the chromosome transformations of the mammals has been shown. The new method of receiving the region-specific DNA-microlibraries has been developed. The DNA-microlibraries, the part of which has been used for the analysis of the chromosome anomalies of the man, have been obtained. The developed methods and DNA-microlibraries are being used in the cytogenetic diagnostics of the chromosome pathologies of the man, in the analysis of the chromosome aberrations in the malignizied cells, at the comparative analysis of the chromosomes of the mammals can be recommended for the introduction in the work of the diagnostic laboratories of medical establishments.Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio