60秒学美语：Bite Me: The Mutation That Made Corn Kernels Consumable

学更多地道英语口语，关注公众微信【英语】微信号：yingyu9 ，如果想系统学习提高英语口语能力，报名吉米老师听力口语特训班，百度传课网chuanke.com 搜索：听力口语特训班，看到第一个即可报名，482个同学报名啦，100%好评哦！ Bite Me: The Mutation That Made Corn Kernels Consumable 快咬我啊 Nothing says summer like a sweet ear of corn. But that treat would be much harder to eat if it weren’t for a crucial mutation. The change, in just one letter of the DNA code, appears to have cracked the hard casing that covered every kernel in corn’s wild ancestor. That’s according to a study in the journal Genetics. [Huai Wang et al, Evidence That the Origin of Naked Kernels During Maize Domestication Was Caused by a Single Amino Acid Substitution in tga1] 夏天怎么也不会像谷粒的甜穗。但是那个东西如果没突变，吃起来还是挺困难的。这种改变，仅仅就是DNA密码子中一个碱基对发生了变化而已，就可以使野生玉米种每隔谷粒外面的外壳崩溃哦。这是根据一项发表在《遗传学》杂志上的研究得出的结论。 Corn was domesticated from a wild grass called teosinte some 9,000 years ago. But how did our ancestors make maize the agricultural marvel it is today? Seems they selectively propagated plants with a particular mutation—one that made the kernels more accessible to hungry Homo sapiens. 玉米是在9000年前从一种名叫teosinte【植】墨西哥类蜀黍的野草驯化过来的。 但是，我们的人类祖先究竟是如何弄出堪称为现代农业奇迹的玉米这种谷类的呢？ 他们好像是通过对一种特别突变体进行选择性繁殖—— 这种体变体可以使智人用玉米仁充饥。 The researchers compared the DNA of 16 varieties of modern corn and 20 types of teosinte. And they found a single, key mutation that is present in modern corn but absent in its wild-grass ancestor. This genetic hiccup disrupts the activity of a protein called tga1. 研究人员们对16种现代玉米和20种墨西哥类蜀黍进行了DNA序列比对。他们发现了一种现代玉米中出现但是古代野生中没有的关键性突变。这种遗传间断干扰了一种名叫tga1的蛋白的活性。 In teosinte, the tga1 protein directs the formation of a hard shell around every corn kernel. But the modern maize mutation gives tga1 a new set of marching orders. The mutant protein turns the ear inside out, converting the seed cases into a cob that holds all the kernels in place. 在墨西哥类蜀黍中， tga1蛋白直接形成一种围绕在每个玉米仁周围的坚硬外壳。但是现代玉米突变体则出现了一系列递进式顺序的tga1蛋白突变体。这种突变的蛋白把玉米穗转到外面，把种子转换成了一个可以支撑整个仁的植物穗。 When the researchers reversed the effects of the mutant protein, the ancestral seed-case remnants started to reappear. 当研究人员们反转突变蛋白现象的时候，原始的包裹种子的残留品种又重现江湖。 The results suggest that even minor genetic changes can lead to some pretty tasty developments. You might call it a-maize-ing. But that would be corny. 结果提示我们，即使很小的遗传变化也能导致出现一些好味道的变化。你可以称之为玉米的奇迹。但是它实际上很老土的。 —Karen Hopkin