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Comparative Cytogenetics. 2007. 1(1): 33-43.

The structural peculiarities of karyotypes in species of Propsilocerus akamusi sibling group (Diptera: Chironomidae)

Kiknadze I.I., Istomina A.G., Golygina V.V., Rubtsov N.B., Karamysheva T.V.

Abstract. First results of the study of karyotype structure, centromeric and peri-centromeric heterochromatin organization in the sibling species P. akamusi Tokunagaand P. jacuticus Zvereva are presented. Karyotypes of these species have an unusualstructure: the centromeric region of each chromosome has 3 large heterochromaticbands of similar morphology. To identify true centromeric bands, C-banding of polytenechromosomes of salivary glands had been performed. Only the central of threeheterochromatic bands in each chromosome in both species showed clear C-bands andcould be identified as centromeric bands. Staining of adjacent heterochromatic bandswas weak. Microdissection of centromeric and adjacent heterochromatic bands ofchromosomes II and III of P. akamusi was performed, and DNA-probes were generatedby DOP-PCR. DNA-probes were hybridized to polytene chromosomes of P. akamusi using the fluorescent in situ hybridization technique (FISH). All probes showed highhomology to the site from which they were originated, and low or no homology to othercentromeric and adjacent heterochromatic bands both within the same chromosomeand the other chromosomes. No signals were detected outside of the centromericregions. Centromeric DNA probe from chromosome II showed low homology tocentromeric regions of chromosomes III, meaning that the centromeric regions of P.akamusi have complex structure, and composition of centromeric DNA differs in differentchromosomes. No signals had been observed from hybridization of P. akamusi DNA-probes with chromosomes of P. jacuticus. So, it is possible to suggest that centromericDNA is strongly divergent between Propsilocerus siblings.