日美科學家在新一期美國《科學》雜志網(wǎng)絡版上發(fā)表論文稱,，他們通過分析青鳉魚脫氧核糖核酸（DNA）的全部信息,，發(fā)現(xiàn)脫氧核糖核酸核小體（染色質的基本結構單位）結構影響著脫氧核糖核酸的變異,，從而影響著生物進化。
東京大學日前發(fā)布新聞公報稱,，這一成果由東京大學和美國斯坦福大學科學家共同獲得,。
公報介紹說，多數(shù)科學家一直用達爾文的進化論和日本科學家木村資生的中性論這兩套互相補充的理論來解釋脫氧核糖核酸發(fā)生的變異,。達爾文進化論的基本原理是,，自然選擇控制生物的進化，大自然將不斷地淘汰不適宜生存的一切有害變異,，只讓有利變異生存下來,。而木村資生在20世紀60年代提出，在分子水平上發(fā)生的基因變異是中性的,，即對生物生存既無益也無害,，自然選擇對它不起作用。日本和美國科學家本次的新發(fā)現(xiàn)使人們對脫氧核糖核酸變異又有了新認識,，這可能是反映脫氧核糖核酸變異新原理的基礎性成果,。
公報說，20世紀90年代后半期,，有研究結果顯示,，脫氧核糖核酸核小體結構有可能影響脫氧核糖核酸的變異?？茖W家發(fā)現(xiàn),，在脫氧核糖核酸堿基修復試驗中，脫氧核糖核酸核小體結構不同,，堿基修復時間也存在顯著差異,。有科學家就猜測，在自然進化過程中,，脫氧核糖核酸的變異或許會因核小體結構的不同而有差別,，但科學家一直沒有獲得直接證據(jù)。
東京大學研究生院教授森下真一和美國斯坦福大學同行在本次研究中借助超高速脫氧核糖核酸解析裝置,，分析青鳉魚所有脫氧核糖核酸核小體結構,，結果證實了過去科學家的猜測。公報認為,，這項研究成果可以部分說明生物遺傳多樣性的產(chǎn)生過程,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science DOI: 10.1126/science.1163183
Chromatin-Associated Periodicity in Genetic Variation Downstream of Transcriptional Start Sites
Shin Sasaki 1, Cecilia C. Mello 2, Atsuko Shimada 3, Yoichiro Nakatani 1, Shin-ichi Hashimoto 4, Masako Ogawa 4, Kouji Matsushima 4, Sam Guoping Gu 2, Masahiro Kasahara 1, Budrul Ahsan 1, Atsushi Sasaki 1, Taro Saito 1, Yutaka Suzuki 5, Sumio Sugano 5, Yuji Kohara 6, Hiroyuki Takeda 3, Andrew Fire 2*, Shinichi Morishita 7*
1 Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277–0882, Japan.
2 Departments of Pathology and Genetics, School of Medicine, Stanford University, Stanford, CA 94305–5324, USA.
3 Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113–0033, Japan.
4 Department of Molecular Preventive Medicine, School of Medicine, The University of Tokyo, Tokyo 113–0033, Japan.
5 Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo 108–8639, Japan.
6 Center for Genetic Resource Information, National Institute of Genetics, Mishima 411–8540, Japan.
7 Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277–0882, Japan.; Bioinformatics Research and Development (BIRD), Japan Science and Technology Agency (JST), Tokyo 102–8666, Japan.
Might DNA sequence variation reflect germline genetic activity and underlying chromatin structure? Using two strains of medaka (Japanese killifish, Oryzias latipes), we compared genomic sequence and mapped ~37.3 million nucleosome cores from medaka Hd-rR blastulae, together with 11,654 representative transcription start sites from six embryonic stages. We observed a ~200–base pair (bp) periodic pattern of genetic variation downstream of transcription start sites; the rate of insertions and deletions longer than 1 bp peaked at positions of approximately +200, +400, and +600 bp, whereas the point mutation rate showed corresponding valleys. This ~200-bp periodicity was correlated with the chromatin structure, with nucleosome occupancy minimized at positions 0, +200, +400, and +600 bp. These data exemplify the potential for genetic activity (transcription) and chromatin structure to contribute in molding the DNA sequence on an evolutionary time scale.
