| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
To elucidate the mechanism of concerted evolution, the evolutionary changes occurred in the Drosophila histone genes have been unveiled. The factors affecting for the concerted evolution were estimated. The repeating units of histone gene in Drosophila were studied for 6 sibling species of D.melanogaster (D.teissieri, D.sechellia, D.mauritiana, D.yakuba, D.orena, and D.erecta) and 5 other species (D.americana, D.lutescens, D.pseudoobscura, D.takahashii, and D.immigrans). In addition, the genetic heterogeneity among the repeating units at the nucleotide sequence level was studied for several species. It was less than 1% and much smaller than the difference between the closely related species. This suggested that the concerted evolution have been observed not only in the H3 gene region but also in the whole repeating unit. Comparison analysis of the GC content in the coding region, 5'-region, 3'-region, and spacer region indicated that no significant difference was observed in the 3'-region and spacer region in where mutation bias was expected more efficiently. In contrast, the species difference was observed in the GC content at the 3^<rd> codon with the same tendency for all histone genes. These results indicated that the natural selection is playing a more important role than the mutation bias. Natural selection against A and T at the GC rich codon was expected, and the efficiency for it depends on the population size. The observed species difference in the GC content can be explained by the different history of the population of the species. This kind of natural selection explains the part of the concerted evolution.
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