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第208期精讲 本文选自经济学人2019年1月17日文章。在过去的数十亿年中，自然界只存在 4 种碱基——腺嘌呤（A）、胸腺嘧啶（T）、胞嘧啶（C）和鸟嘌呤。现在，研究人员打破了这些规则，在 Floyd Romesberg 位于圣地亚哥的实验室，科学家通过扩展基因编码，在培养的细菌中增加了一对“超自然”的碱基对：X 和 Y。更令人惊奇的是，细菌可以利用这对超自然碱基对编码新蛋白！这一突破一举改变了大众对于生命遗传信息的认知，堪称“颠覆遗传密码”的成果。 由于篇幅较长，本文节选原文标题和全文重点段落进行精讲，帮助大家提高英语阅读和写作能力。
01 英文原文 Extending the genetic code Adding new DNA letters make novel proteins possible One such, a cancer drug, is now in development  Jan 17th 2019 | LA JOLLA, CALIFORNIA THE FUZZY specks growing on discs of jelly in Floyd Romesberg’s lab at Scripps Research in La Jolla look much like any other culture of E. coli. But appearances deceive—for the DNA of these bacteria is written in an alphabet that has six chemical letters instead of the usual four. Every other organism on Earth relies on a quartet of genetic bases: A (adenine), C (cytosine), T (thymine) and G (guanine). These fit together in pairs inside a double-stranded DNA molecule, A matching T and C, G. But in 2014 Dr Romesberg announced that he had synthesised a new, unnatural, base pair, dubbed X and Y, and slipped them into the genome of E. coli as well. Kept supplied with sufficient quantities of X and Y, the new cells faithfully replicated the enhanced DNA—and, crucially, their descendants continued to do so, too. Since then, Dr Romesberg and his colleagues have been encouraging their new, “semisynthetic” cells to use the expanded alphabet to make proteins that could not previously have existed, and which might have properties that are both novel and useful. Now they think they have found one. In collaboration with a spin-off firm called Synthorx, they hope to create a less toxic and more effective version of a cancer drug called interleukin-2.
02 选文精读 Extending the genetic code 扩展遗传密码 Adding new DNA letters make novel proteins possible 新增的DNA碱基让产生新的蛋白质成为可能
One such, a cancer drug, is now in development 其中一种抗癌药物正在研发中 THE FUZZY specks growing on discs of jelly in Floyd Romesberg’s lab at Scripps Research in La Jolla look much like any other culture of E. coli. But appearances deceive—for the DNA of these bacteria is written in an alphabet that has six chemical letters instead of the usual four.
在拉霍亚的斯克里普斯研究中心的弗洛伊德·罗梅斯伯格的实验室里，胶盘上生长着的模糊的斑点看起来很像大肠杆菌培养物。不要被它的外表欺骗了，因为这些细菌的DNA是用6个碱基字母组成，而不是通常的4个。 Every other organism on Earth relies on a quartet of genetic bases: A (adenine), C (cytosine), T (thymine) and G (guanine). These fit together in pairs inside a double-stranded DNA molecule, A matching T and C, G. But in 2014 Dr Romesberg announced that he had synthesised a new, unnatural, base pair, dubbed X and Y, and slipped them into the genome of E. coli as well.
地球上的其他所有生物都是基于四种碱基：A(腺嘌呤)、C(胞嘧啶)、T(胸腺嘧啶)和G(鸟嘌呤)。它们成对地组合在一个双链DNA分子中，A和T配对, C和G配对。但是2014年，Romesberg博士宣布他已经合成了一个新的，超自然的碱基对，称为X和Y，并将它们植入大肠杆菌的基因组中。 Kept supplied with sufficient quantities of X and Y, the new cells faithfully replicated the enhanced DNA—and, crucially, their descendants continued to do so, too. Since then, Dr Romesberg and his colleagues have been encouraging their new, “semisynthetic” cells to use the expanded alphabet to make proteins that could not previously have existed, and which might have properties that are both novel and useful. Now they think they have found one. In collaboration with a spin-off firm called Synthorx, they hope to create a less toxic and more effective version of a cancer drug called interleukin-2.
如果提供足够数量的X和Y，新细胞会不停的复制强化的DNA——关键的是，它们的后代也会不停的复制。此后，Romesberg博士和他的同事们一直在尝试用这种新的，“半合成”细胞使用新增的碱基来制造以前不存在的蛋白质，而这些蛋白质可能具有新的和有用的特性。现在他们认为自己到了一个。他们与一家名为Synthorx的分拆公司合作，希望开发出一种毒性更小、更有效的抗癌药物——白介素-2。 |
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