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          人類DNA中只有8.2%有用 其余的都無所事事

          作者:admin 發表于:2014-07-26 點擊:1139  保護視力色:
          牛津大學一項研究得出結論認為我們的DNA中只有8.2%有可能做一些重要的事情。其余的都是無用DNA,一種進化遺留產物,很像盲腸,沒有任何好處,但也沒有任何害處。


          科學探索

           
          PLOS Genetics:人類DNA中只有8.2%有用 其余的都無所事事
           

            牛津大學一項研究得出結論認為我們的DNA中只有8.2%有可能做一些重要的事情。其余的都是無用DNA,一種進化遺留產物,很像盲腸,沒有任何好處,但也沒有任何害處。其中很大一部分不做任何事情。

            這項研究的聯合首席研究員Gurton Lunter博士說:“絕大多數是坐在那里無所事事,它占用空間?!?/P>

            先前估計我們的DNA中有80%是‘有用的’或者做一些有用的事?!皬尼t學角度講,這是必不可少的解釋人類疾病中遺傳變異的作用”。而研究人員在比較了我們與其他哺乳動物的DNA后提出8.2%的估計,并尋找雖然經歷了數百萬年的進化任然保持不變的區塊。

            這種沒有變化被看作為一種標志它做著一些重要的事情。更重要的是,雖然通常認為我們的DNA充滿了基因,但是8%中只有超過1%是有用的遺傳物質。其他的7%左右是散落著的控制這些基因的開關。

            研究人員Chris Rands 說:“我們往往傾向于我們所有的DNA都必須做點什么。而現實是只有一小部分有功能?!?來源:生物幫)


            原文摘要:

          8.2% of the Human Genome Is Constrained: Variation in Rates of Turnover across Functional Element Classes in the Human Lineage

          Chris M. Rands, Stephen Meader, Chris P. Ponting, Gerton Lunter

            Ten years on from the finishing of the human reference genome sequence, it remains unclear what fraction of the human genome confers function, where this sequence resides, and how much is shared with other mammalian species. When addressing these questions, functional sequence has often been equated with pan-mammalian conserved sequence. However, functional elements that are short-lived, including those contributing to species-specific biology, will not leave a footprint of long-lasting negative selection. Here, we address these issues by identifying and characterising sequence that has been constrained with respect to insertions and deletions for pairs of eutherian genomes over a range of divergences. Within noncoding sequence, we find increasing amounts of mutually constrained sequence as species pairs become more closely related, indicating that noncoding constrained sequence turns over rapidly. We estimate that half of present-day noncoding constrained sequence has been gained or lost in approximately the last 130 million years (half-life in units of divergence time, d1/2 = 0.25–0.31). While enriched with ENCODE biochemical annotations, much of the short-lived constrained sequences we identify are not detected by models optimized for wider pan-mammalian conservation. Constrained DNase 1 hypersensitivity sites, promoters and untranslated regions have been more evolutionarily stable than long noncoding RNA loci which have turned over especially rapidly. By contrast, protein coding sequence has been highly stable, with an estimated half-life of over a billion years (d1/2 = 2.1–5.0). From extrapolations we estimate that 8.2% (7.1–9.2%) of the human genome is presently subject to negative selection and thus is likely to be functional, while only 2.2% has maintained constraint in both human and mouse since these species diverged. These results reveal that the evolutionary history of the human genome has been highly dynamic, particularly for its noncoding yet BioLogically functional fraction.

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