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But they will do that in a very particular way, in that only strands that exactly match will be able to reform their native structure.
但是双链的形成也不是随意的,只有完全互补的单链之间,才成重新恢复到它们原先的结构
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They're colored different here to indicate one new difference that you know about now, and that's that there is an orientation, there's an up and down on the chain.
这里被涂成不同的颜色,来表示另一个不同之处,它是有方向的,表示双链一条向上,一条向下
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This notion of complementary strands is very important.
这个双链互补配对的概念非常重要
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You can do that by gently adding heat and making it basic, but you make the two DNA strands separate.
你可以通过逐渐加温并使之碱化的方法,使双链DNA解旋
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Certain double stranded RNA sequences will cause in the cell a process of degradation of very specific RNA sequence.
一些双链RNA序列能够在细胞中开启,特定RNA序列的降解程序
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You put this chromosomal DNA or this DNA that you're interested in, double stranded into a test tube.
你把这个染色体DNA,或者你感兴趣的双链的DNA,放进一个试管
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The end result of transcription is not double stranded DNA, it's single stranded RNA where the RNA that's produced is called messenger RNA.
最终的转录产物并非双链的DNA,而是单链的RNA,称为信使RNA
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The DNA molecule here has been spread apart, opening up two single stranded DNA's which have complementary base sequences because they were double stranded DNA.
这里DNA分子被分开,形成两条单链DNA,这两条单链碱基序列互补,因为它们是由双链DNA解旋形成的
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I'm going to start by talking about a very specific and interesting form of double stranded DNA called a plasmid and plasmids occur in nature.
我要从一种十分特殊,并有趣的双链DNA开始,这种双链DNA被称为质粒,它在自然界就存在
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The result of this process if this replication went down the whole length of the DNA would be to form two identical, double stranded DNA molecules.
如果复制过程在整条链上持续进行的话,将生成两条完全一样的,双链DNA分子
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Now, in your book, there's an example of plasmid where I've given you the exact sequence of nucleotides that makes up the whole double stranded DNA molecule.
现在在你们书里,有个质粒样本,我将组成这个双链DNA分子的,核苷酸序列写在这里了
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If I took two double stranded DNA molecules and I exposed them to certain conditions that caused them to denature, that means its native structure falls apart.
假如我把两条DNA双链,放在特定的条件下,使它们变性,变性表示使它们的原始结构分开
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That only strands that have this exact complement can form double stranded DNA.
这表示只有两条链的碱基对,完全互补才能形成DNA双链
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It has to do with the nature of this complementary binding between double stranded DNA and the fidelity of this base pair matching in forming stable DNA molecules.
这些特性能从根本上解释,为何DNA双链的碱基能互补配对,以及在形成稳定的DNA分子结构时,碱基互补配对为何具有一致性
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That tells you something about the physical chemistry of the molecule; that it's these hydrogen bonds that hold the double strands and I can break those down under certain conditions.
我们从中可以知道一些,DNA分子的理化特点,双链是由氢键连接在一起,在一定条件下这些氢键可以断裂
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That's because you have to satisfy this base pair matching in order to have hydrogen bonding in each of the struts of the ladder in order to form a stable structure.
NA双链要满足互补配对原则,以使碱基对之间,形成氢键,从而形成稳定的双链结构
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When they separate, the primers that you've added automatically bind through the process of hybridization, and then you turn up the temperature to the optimum for Taq polymerase and DNA synthesis starts.
当双链解旋后,加入的引物就会在杂交的步骤中自动,和解旋后的DNA结合,然后你再将温度升高至,Taq酶的最适温度,DNA就开始合成了
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The end result is you can design now very specific double stranded RNA sequences, that when delivered into cells again will activate this process of natural degradation of an existing messenger RNA.
最终的结果是,你现在能够设计针对性很强的,双链RNA序列,当这段序列被转入细胞后会激活,对已有信使RNA进行降解的过程
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When it's double stranded this gene can't be translated, because you have to have the single strand in order for the transfer RNA to bind and for this process of translation to take place.
当基因处于双链结构状态时,是不能进行翻译的,因为必须把双链拆开得到单链,才能结合转运RNA并开始翻译过程
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Remember we talked about how DNA replicates itself and that there are enzymes, DNA polymerase that bind to the double stranded DNA, separate it, denature it locally, and then start the process of replication.
请记住DNA复制必须有酶的参与,DNA聚合酶结合在双链DNA上,打开双链并原位变性,然后才开始复制
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The first step is to take the DNA fragments that we're interested in and put them into this vector by basically cutting open the double stranded DNA and inserting the gene that we like in the region where we've cut.
第一步是把我们感兴趣的DNA片段,整合到这个载体里,基本的方法是切开质粒这个双链DNA,把我们想要的基因插入切开的区域
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It operates in a similar fashion to DNA polymerase in that it denatures locally or opens up the double stranded DNA, but it's different in that it creates a new polymer from the DNA template in the language of RNA, using RNA nucleotides and not DNA nucleotides.
它的作用机制类似于DNA聚合酶,在局部使DNA双链变性,解旋,但不同的是,它合成了一个基于DNA模板的,使用RNA编码语言的新聚合物,即使用核糖核苷而非脱氧核糖核苷
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Now the nice thing about this is that the degradation mechanisms seem to persist for some period of time, beyond the time at which you deliver the double stranded RNA; whereas, obviously, this mechanism here is only going to exist for as long as the anti-sense sequence is present.
而好消息是降解过程会持续一段时间,比你转入双链RNA的时间要长,但是,这种机制只会在,有反义链的时候发挥作用
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