最新Nature公布又一重要基因组

【字体: 时间:2008年11月21日 来源:生物通

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生物通报道:在上周《Nature》《Science》公布了三角褐指藻(Phaeodactylum tricornutum)和白蚁(Pseudotrichonympha grassii)的基因组之后,本周(11月20日)《Nature》又公布了80%猛犸象的基因组。

据新浪科技报道,科学家通过已在西伯利亚永久冻结带冷冻数千年的两具猛犸象尸体提取的毛发样本,整理出这种史前巨兽的DNA。基因代码让科学家对猛犸象的进化过程有了新的了解,同时表明它们远比之前想象的更接近于现代象。这项发现还可以使研究人员搞清楚大象的遗传构造,复活灭绝已久的猛犸象。

这项研究表明,两头猛犸象关系十分紧密。另外分析还表明,600万年前,猛犸象和现代象走向了不同的进化路径,几乎与此同时,人类和黑猩猩也走上了与它们一样的进化道路。200万年前,猛犸象一分为二,一组在距今4.5万年前灭绝,另一组在距今1万年前最后一个冰河时期的末期从地球上消失。

雄性猛犸象高约10英尺(约合3米),雌性相对矮一些。它们的尖牙长而弯曲,腹部的毛发最长可达3英尺(约合0.9米)。迄今,科学家已在西伯利亚发现了大约40具猛犸象的尸体。实施最新研究的美国科学家之所以使用提取自猛犸象毛发的DNA,是因为相对于猛犸象尸体其他部位的DNA,它们保存得更为完好。

一些研究人员一直建议使用冰冻猛犸象尸体的皮肤或毛发克隆猛犸象。领导这项研究的宾夕法尼亚州立大学教授史蒂芬·舒斯特(Stephan Schuster)说:“从理论上讲,通过破译这个基因组,我们可以获取重要的信息,将来有一天,只要将独特的猛犸象DNA序列融入现代象的基因组中,这些信息或能帮助其他研究人员复活猛犸象。”

但是,西澳大利亚默多克大学古生物DNA实验室主任迈克尔·邦斯(Michael Bunce)博士给舒斯特教授泼了一瓢凉水。他说:“掌握某种生物的DNA代码并不意味着我们可以通过遗传手段实现重造灭绝生物体的美好愿望。”

原文摘要:

Sequencing the nuclear genome of the extinct woolly mammoth

In 1994, two independent groups extracted DNA from several Pleistocene epoch mammoths and noted differences among individual specimens1, 2. Subsequently, DNA sequences have been published for a number of extinct species. However, such ancient DNA is often fragmented and damaged3, and studies to date have typically focused on short mitochondrial sequences, never yielding more than a fraction of a per cent of any nuclear genome. Here we describe 4.17 billion bases (Gb) of sequence from several mammoth specimens, 3.3 billion (80%) of which are from the woolly mammoth (Mammuthus primigenius) genome and thus comprise an extensive set of genome-wide sequence from an extinct species. Our data support earlier reports4 that elephantid genomes exceed 4 Gb. The estimated divergence rate between mammoth and African elephant is half of that between human and chimpanzee. The observed number of nucleotide differences between two particular mammoths was approximately one-eighth of that between one of them and the African elephant, corresponding to a separation between the mammoths of 1.5–2.0 Myr. The estimated probability that orthologous elephant and mammoth amino acids differ is 0.002, corresponding to about one residue per protein. Differences were discovered between mammoth and African elephant in amino-acid positions that are otherwise invariant over several billion years of combined mammalian evolution. This study shows that nuclear genome sequencing of extinct species can reveal population differences not evident from the fossil record, and perhaps even discover genetic factors that affect extinction.

 

 

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