转录（Transcription）是遗传信息从DNA流向RNA的过程。即以双链DNA中的确定的一条链（模板链用于转录，编码链不用于转录）为模板，以A、U、C、G四种核糖核苷酸为原料，在RNA聚合酶催化下合成RNA的过程。作为蛋白质生物合成的第一步，进行转录时，一个基因会被读取并被复制为mRNA，即特定的DNA片段作为遗传信息模板，以依赖DNA的RNA聚合酶作为催化剂，通过碱基互补的原则合成前体mRNA。RNA聚合酶通过与一系列组分构成动态复合体，完成转录起始、延伸、终止等过程。生成的mRNA携有的密码子，进入核糖体后可以实现蛋白质的合成。转录仅以DNA的一条链作为模板，被选为模板的单链称为模板链，亦称无义链；另一条单链称为非模板链，即编码链，因编码链与转录生成的RNA序列T变为U外其他序列一致，所以又称有义链。DNA上的转录区域称为转录单位。

Now that we've covered DNA replication let's talk about Transcription.
现在,我们已经讲解了DNA复制,接下来我们来讲解转录·
The first thing you need to know is that transcription has nothing to do with cell replication processes such as DNA replication mitosis or cell division.
首先,您需要知道的是,转录与细胞复制过程(如DNA复制、有丝分裂或细胞分裂)无关·
So what is transcription and why is it necessary
那么,什么是转录?为什么它是必要的?
Well transcription is the first step in the process of using the genetic code in DNA to synthesize or build all the different proteins in your body.
转录是利用DNA中的遗传密码合成或构建体内所有不同蛋白质的过程中的第一步·
One problem with synthesizing these proteins is that the instructions for making them are in the DNA which is located inside the nucleus.
合成这些蛋白质的一个问题是,制造它们的指令在DNA中,而DNA位于细胞核内·
But the place proteins are always made is outside the nucleus either in the ribosomes floating in the cytoplasm or in the ribosomes embedded in the rough endoplasmic reticulum.
但是,蛋白质总是在细胞核外制造,要么在漂浮在细胞质中的核糖体中,要么在粗面内质网中的嵌入式核糖体中·
So how does the genetic code for synthesizing proteins get from the DNA to the ribosome
那么,合成蛋白质的遗传密码是如何从DNA传递到核糖体的?
DNA uses a messenger called messenger RNA or mRNA to carry the genetic code from the nucleus to the ribosome.
DNA使用一种叫做信使RNA(mRNA)的信使,将遗传密码从细胞核传递到核糖体·
The process of building this messenger RNA is called Transcription.
构建这种信使RNA的过程叫做转录·
Now let's see how transcription happens.
现在,让我们看看转录是如何发生的·
Transcription begins when an enzyme called RNA polymerase attaches to a segment of DNA called a gene.
转录开始时,一种叫做RNA聚合酶(RNA polymerase)的酶附着在DNA的一段区域上,这个区域叫做基因·
A gene contains the code to build a specific protein which is a macromolecule made up of a sequence of amino acids in a specific order.
基因包含构建特定蛋白质的密码,蛋白质是由一系列特定顺序的氨基酸组成的大分子·
And within a gene the specific order of nitrogenous bases dictates the order of amino acids that will make up the protein.
在基因内部,氮碱基的特定顺序决定了将构成蛋白质的氨基酸的顺序·
Each group of three consecutive bases in the gene is actually a code for a particular amino acid.
基因中每三个连续的碱基组成的组实际上是特定氨基酸的编码·
As a result each group is referred to as a codon.
因此,每个组被称为密码子(codon)·
RNA polymerase causes a particular area of the DNA helix to unwind and separate into two strands.
RNA聚合酶使DNA螺旋的特定区域解开并分离成两条链·
One of the strands often called the template strand is the side of DNA that is read or transcribed by the messenger RNA.
其中一条链,通常称为模板链,是DNA的一侧,信使RNA会读取或转录它·
The other strand of DNA often called the non template strand isn't transcribed by the messenger RNA.
另一条DNA链,通常称为非模板链,并不会被信使RNA转录·
So how are DNA instructions transcribed into messenger RNA
那么,DNA中的指令是如何转录成信使RNA的呢?
Well using the template strand as a guide
通过使用模板链作为指南,
RNA polymerase uses the base pair rule to assemble free nucleotides in the nucleus into a complementary strand of RNA.
RNA聚合酶按照碱基配对规则,在细胞核中将自由核苷酸组装成互补的RNA链·
For example RNA polymerase reads the DNA base thymine on the template strand then binds it to a free nucleotide containing adenine.
例如,RNA聚合酶读取模板链上的DNA碱基胸腺嘧啶(T),然后将它与含有腺嘌呤(A)的自由核苷酸配对·
This process continues with cytosine binding to guanine and guanine binding with cytosine.
这个过程继续进行,胞嘧啶(C)与鸟嘌呤(G)配对,鸟嘌呤(G)与胞嘧啶(C)配对·
Remember though RNA will never contain thymine.
但请记住,RNA永远不会包含胸腺嘧啶(T)·
So whenever RNA polymerase sees adenine on the DNA template strand it pairs adenine with uracil.
因此,每当RNA聚合酶在DNA模板链上看到腺嘌呤(A)时,它会将腺嘌呤与尿嘧啶(U)配对·
By using the template strand of DNA as a guide
通过使用DNA的模板链作为指南,
the genetic code from the non template strand of DNA has actually been transcribed into messenger RNA.
来自DNA非模板链的遗传密码实际上已经被转录成信使RNA·
When transcription is complete
当转录完成时,
the messenger RNA which is small enough to fit through a nuclear pore
信使RNA(足够小,可以通过核孔)
takes the genetic code out of the nucleus to the ribosome the site of protein synthesis.
将遗传密码带出细胞核,传递到核糖体,那里是蛋白质合成的地方·
The process of actually building the protein at the ribosome is called Translation which we'll cover in a separate video.
在核糖体上实际构建蛋白质的过程叫做翻译(Translation),我们将在另一个视频中讲解翻译过程·
To summarize transcription is the process of transcribing or copying the genetic code for building a protein into messenger RNA.
总结一下,转录是将构建蛋白质的遗传密码转录或复制成信使RNA的过程·
A gene is a segment of DNA containing the instructions or code for building a protein.
基因是DNA的一段区域,包含构建蛋白质的指令或编码·
A codon is a group of three consecutive nitrogenous bases in a gene containing the code for a specific amino acid in a protein.
密码子是基因中由三个连续的氮碱基组成的组,包含蛋白质中特定氨基酸的编码·
RNA polymerase unwinds the strands of DNA in a gene.
RNA聚合酶解开基因中的DNA链·
The template DNA strand contains the complementary bases that need to be read to generate messenger RNA.
模板DNA链包含需要被读取的互补碱基,以生成信使RNA·
The base pair rule is followed when assembling messenger RNA.
在组装信使RNA时遵循碱基配对规则·
Messenger RNA is actually a copy of the DNA non template strand with uracil substituted for thymine.
信使RNA实际上是DNA非模板链的副本,尿嘧啶(U)替代了胸腺嘧啶(T)·
内容操作
视频
教程课件
单词卡片