engleski

Long range organization and evolution of heterochromatic DNA

Study of heterochromatic DNA structure and organization is necessary for determination of centromere identity and function. In addition, significant differences in structure and organization of heterochromatic DNA, even between closely related species, points to its possible role in the evolution of species. In mollusc Donax trunculus four related, low copy number satellites are present. Uninterrupted satellite arrays are organized in fragments ranging in size from 50-400 kb linked by the region of complex, nonrepetitive DNA. Different type of heterochromatin organization is found in the insect Pimelia criba (Tenebrionidae, Coleoptera) where a single satellite comprises 40% of genomic DNA. The most of the satellite is organized in clusters with approx. size between 200-700 kb. Strong hybridization signal above 2.2 Mb points to the existence of even larger satellite arrays. However, in tenebrionid species, low copy number satellites dispersed between the large arrays of highly abundant, major satellites dispersed between the large arrays of highly abundant, major satellite DNA are detected. Comparison of satellite profiles among related species reveals sequence conservation despite high difference in the amount of particular satellite. Such a pattern explains satellite DNA evolution confirming the hypothesis that related species share a library of conserved satellite sequences. Quantitative changes in satellite DNAs could possibly occur in the course of speciation process, thus forming species specific profile of satellite DNA.

satellite DNA; genome organization

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