LATE-REPLICATING REGIONS IN SALIVARY GLAND POLYTENE CHROMOSOMES OF DROSOPHILA MELANOGASTER
T.D. Kolesnikova, N.G. Andreyenkova, E.S. Belyaeva, F.P Goncharov,
T.Yu. Zykova, L.V. Boldyreva, G.V. Pokholkova, I.F. Zhimulev
Institute of Molecular and Cellular Biology SB RAS, Novosibirsk;
e-mail: zhimulev@mcb.nsc.ru
About 240 specific regions are identified on D. melanogaster polytene chromosomes which are replicated at the very end of the S-phase. They have a repressive
chromatine state, low gene density, long intergenic distances and are enriched in tissue specific genes. In polytene chromosomes, about a quarter of these regions have no
enough time to complete replication, as a result, underreplication zones, represented by less DNA copy number, appear. We studied 60 chromosome regions that demonstrate
more pronounced underreplication. Having compared location of these regions on a molecular map and syntenic blocks found earlier for Drosophila species by von
Grotthuss et al., 2010, we have shown that across the genus Drosophila these regions tend to have conserved gene order. It makes us to propose existence of evolutionary
mechanisms directed to maintain the integrity of these regions.
Key words: Drosophila, late replication, polytene chromosomes, underreplication, intercalary heterochromatin, synteny blocks
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