Climate change is partly to blame, but also dams upstream on the Mekong River that choke the flow of freshwater.

气候变化是部分原因，但湄公河上游的大坝也阻遏了淡水的流动。

The lactose you'll notice is going to fit perfectly into that repressor.

你会注意到，乳糖会完美地嵌入到那个阻遏蛋白中。

In other words, now the repressor doesn't fit in the operator anymore.

换言之，现在阻遏蛋白无法再与操纵子结合。

And when it fits in the repressor it changes the confirmation or the shape of that protein.

当它（诱导物）与阻遏蛋白结合时，会改变该蛋白质的构象或形。

And so the way it works here is that the actual tryptophan fits in the repressor.

原理是，实际的色氨酸会与阻遏蛋白结合。

Well now the repressor is going to change shape.

现在，阻遏蛋白即将改变形。

The other thing that I'm going to add here is something called a repressor.

我要在这里补充的另一个概念是“阻遏蛋白”。

So now the lactose is gone and what's happening to our repressor?

现在乳糖已经消失了，我们的阻遏蛋白会发生什么变化呢？

And so this would be, when the repressor is here the operator is now in the off position.

因此，当阻遏蛋白在此处时，操纵子处于关闭态。

This repressor I'm going to show you is showing what's called positive control.

我要展示给你们的这种阻遏蛋白，体现的是所谓的正调控机制。

We're going to get rid of that repressor and we continue.

我们将去除那个阻遏蛋白，然后继续。

One sharp contributor, Aqil Shah, reckons that Pakistan will become “neither Sweden nor Somalia”, as the army's strong grip will prevent disintegration but also block growth of strong civilian institutions.

Aqil Shah认为巴基斯坦不会步瑞士和索马里后尘，军队紧握政权使免于风崩离新的可能，但也阻遏了平民机构的强劲增长。

The NATO Military Alliance has approved the request from Turkey for Patriot intercept missiles to counter any threat from across its border with Syria.More shells from Syrian conflict landed inside Turkey on Tuesday.

北约军事同盟批准了土尔使用爱国者拦截导弹，以阻遏来自于邻国叙利亚的任何威胁。周三在土尔境内落入了更多来自于叙利亚战斗的炮弹。

A repressor will plug right into the operator, so it's going to fit right here, and as long as the repressor is available, RNA polymerase can't get on.

阻遏蛋白会正好嵌入操纵子中，因此它将恰好适应这里， 只要阻遏蛋白存在，RNA聚合酶就无法进入。

And then finally I'll show you what we know about eukaryotic gene regulation and how they use transcription factors as activators, repressors to either express a gene or not.

最后， 我将向您展示我们对真核生物基因调控的了解， 以及它们如何利用转录因子为激活剂或阻遏蛋白，来决定是否表达某个基因。