When it cuts it leaves sticky ends or un-base paired single stranded regions on each end of the part its cut and that's just a property of many restriction enzymes; not all, some cut blunt,just right down the middle.
它切割后会留下两个粘性末端,或者未配对的单链部分,这是许多限制性内切酶的特性,但不是全部,有些限制性内切酶是从中间钝切的
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
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
Transcription just means making a single stranded RNA copy of a sequence of base pairs in a DNA.
转录的过程就是从一段DNA碱基序列中,复制出一段单链RNA
When it sees that sequence in a double stranded DNA it will bind there and it will cut.
当它在双链DNA中发现这个序列,就会与之结合并切割
This is - what this diagram shows you is-- the forces that hold these individual strands of DNA into a double stranded form.
你们可以看看这个图表,演示了连接两条DNA长链为双螺旋,结构的化学力
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
It exists in a double stranded form where every strand is matched by its complement.
这种碱基配对存在于DNA双链中,每条单链都与其互补链,通过这个原则配对组合
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
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
It turns out to activate RNA interference, you deliver double stranded RNA.
要激活RNA干扰效应的话,可以将双链RNA转进细胞
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
It turns out that we can do that now because we have an enzyme called reverse transcriptase, which is able to take single stranded messenger RNA and make DNA out of it.
我们现在已经可以做到这一点了,因为我们有了反转录酶,反转录酶可以用,单链的mRNA创造出DNA
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
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
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
If I had a beaker sitting on the table here and it contained a million blue double stranded DNA molecules and a million red double stranded DNA molecules and I heated it up and added a little base, I'd soon have four million individual strands just floating around in the solution because I've broken up this hydrogen bonding and the DNA molecules fall apart.
假如我这里有一个烧杯 里面,盛有一百万条蓝色DNA双链和,一百万条红色DNA双链,然后我稍微加热一下烧杯,并且加一些碱,很快我就有了四百万条DNA单链,漂浮在溶液里,因为我已经使得氢键断裂,DNA双链也随之打开
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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