得得啪在线视频观看|免费污苹果香蕉荔枝丝瓜IOS|欧美日韩中文字幕完整版|国产精品v欧美精品v日韩精品|久草热8精品视频在线观看|强上轮流草的合不拢腿|岳把我用嘴含进满足我视频

轉(zhuǎn)錄（Transcription）是遺傳信息從DNA流向RNA的過(guò)程。即以雙鏈DNA中的確定的一條鏈（模板鏈用于轉(zhuǎn)錄，編碼鏈不用于轉(zhuǎn)錄）為模板，以A、U、C、G四種核糖核苷酸為原料，在RNA聚合酶催化下合成RNA的過(guò)程。作為蛋白質(zhì)生物合成的第一步，進(jìn)行轉(zhuǎn)錄時(shí)，一個(gè)基因會(huì)被讀取并被復(fù)制為mRNA，即特定的DNA片段作為遺傳信息模板，以依賴DNA的RNA聚合酶作為催化劑，通過(guò)堿基互補(bǔ)的原則合成前體mRNA。RNA聚合酶通過(guò)與一系列組分構(gòu)成動(dòng)態(tài)復(fù)合體，完成轉(zhuǎn)錄起始、延伸、終止等過(guò)程。生成的mRNA攜有的密碼子，進(jìn)入核糖體后可以實(shí)現(xiàn)蛋白質(zhì)的合成。轉(zhuǎn)錄僅以DNA的一條鏈作為模板，被選為模板的單鏈稱為模板鏈，亦稱無(wú)義鏈；另一條單鏈稱為非模板鏈，即編碼鏈，因編碼鏈與轉(zhuǎn)錄生成的RNA序列T變?yōu)閁外其他序列一致，所以又稱有義鏈。DNA上的轉(zhuǎn)錄區(qū)域稱為轉(zhuǎn)錄單位。

內(nèi)容操作
視頻
教程課件
單詞卡片
Now that we've covered DNA replication let's talk about Transcription
現(xiàn)在,我們已經(jīng)講解了DNA復(fù)制,接下來(lái)我們來(lái)講解轉(zhuǎn)錄·
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,轉(zhuǎn)錄與細(xì)胞復(fù)制過(guò)程(如DNA復(fù)制、有絲分裂或細(xì)胞分裂)無(wú)關(guān)·
So what is transcription and why is it necessary
那么,什么是轉(zhuǎn)錄?為什么它是必要的?
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
轉(zhuǎn)錄是利用DNA中的遺傳密碼合成或構(gòu)建體內(nèi)所有不同蛋白質(zhì)的過(guò)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
合成這些蛋白質(zhì)的一個(gè)問(wèn)題是,制造它們的指令在DNA中,而DNA位于細(xì)胞核內(nèi)·
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,蛋白質(zhì)總是在細(xì)胞核外制造,要么在漂浮在細(xì)胞質(zhì)中的核糖體中,要么在粗面內(nèi)質(zhì)網(wǎng)中的嵌入式核糖體中·
So how does the genetic code for synthesizing proteins get from the DNA to the ribosome
那么,合成蛋白質(zhì)的遺傳密碼是如何從DNA傳遞到核糖體的?
DNA uses a messenger called messenger RNA or mRNA to carry the genetic code from the nucleus to the ribosome
DNA使用一種叫做信使RNA(mRNA)的信使,將遺傳密碼從細(xì)胞核傳遞到核糖體·
The process of building this messenger RNA is called Transcription
構(gòu)建這種信使RNA的過(guò)程叫做轉(zhuǎn)錄·
Now let's see how transcription happens
現(xiàn)在,讓我們看看轉(zhuǎn)錄是如何發(fā)生的·
Transcription begins when an enzyme called RNA polymerase attaches to a segment of DNA called a gene
轉(zhuǎn)錄開(kāi)始時(shí),一種叫做RNA聚合酶(RNA polymerase)的酶附著在DNA的一段區(qū)域上,這個(gè)區(qū)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
基因包含構(gòu)建特定蛋白質(zhì)的密碼,蛋白質(zhì)是由一系列特定順序的氨基酸組成的大分子·
And within a gene the specific order of nitrogenous bases dictates the order of amino acids that will make up the protein
在基因內(nèi)部,氮堿基的特定順序決定了將構(gòu)成蛋白質(zhì)的氨基酸的順序·
Each group of three consecutive bases in the gene is actually a code for a particular amino acid
基因中每三個(gè)連續(xù)的堿基組成的組實(shí)際上是特定氨基酸的編碼·
As a result each group is referred to as a codon
因此,每個(gè)組被稱為密碼子(codon)·
RNA polymerase causes a particular area of the DNA helix to unwind and separate into two strands
RNA聚合酶使DNA螺旋的特定區(qū)域解開(kāi)并分離成兩條鏈·
One of the strands often called the template strand is the side of DNA that is read or transcribed by the messenger RNA
其中一條鏈,通常稱為模板鏈,是DNA的一側(cè),信使RNA會(huì)讀取或轉(zhuǎn)錄它·
The other strand of DNA often called the non template strand isn't transcribed by the messenger RNA
另一條DNA鏈,通常稱為非模板鏈,并不會(huì)被信使RNA轉(zhuǎn)錄·
So how are DNA instructions transcribed into messenger RNA
那么,DNA中的指令是如何轉(zhuǎn)錄成信使RNA的呢?
Well using the template strand as a guide
通過(guò)使用模板鏈作為指南,
RNA polymerase uses the base pair rule to assemble free nucleotides in the nucleus into a complementary strand of RNA
RNA聚合酶按照堿基配對(duì)規(guī)則,在細(xì)胞核中將自由核苷酸組裝成互補(bǔ)的RNA鏈·
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聚合酶讀取模板鏈上的DNA堿基胸腺嘧啶(T),然后將它與含有腺嘌呤(A)的自由核苷酸配對(duì)·
This process continues with cytosine binding to guanine and guanine binding with cytosine
這個(gè)過(guò)程繼續(xù)進(jìn)行,胞嘧啶(C)與鳥(niǎo)嘌呤(G)配對(duì),鳥(niǎo)嘌呤(G)與胞嘧啶(C)配對(duì)·
Remember though RNA will never contain thymine
但請(qǐng)記住,RNA永遠(yuǎn)不會(huì)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,每當(dāng)RNA聚合酶在DNA模板鏈上看到腺嘌呤(A)時(shí),它會(huì)將腺嘌呤與尿嘧啶(U)配對(duì)·
By using the template strand of DNA as a guide
通過(guò)使用DNA的模板鏈作為指南,
the genetic code from the non template strand of DNA has actually been transcribed into messenger RNA
來(lái)自DNA非模板鏈的遺傳密碼實(shí)際上已經(jīng)被轉(zhuǎn)錄成信使RNA·
When transcription is complete
當(dāng)轉(zhuǎn)錄完成時(shí),
the messenger RNA which is small enough to fit through a nuclear pore
信使RNA(足夠小,可以通過(guò)核孔)
takes the genetic code out of the nucleus to the ribosome the site of protein synthesis
將遺傳密碼帶出細(xì)胞核,傳遞到核糖體,那里是蛋白質(zhì)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
在核糖體上實(shí)際構(gòu)建蛋白質(zhì)的過(guò)程叫做翻譯(Translation),我們將在另一個(gè)視頻中講解翻譯過(guò)程·
To summarize transcription is the process of transcribing or copying the genetic code for building a protein into messenger RNA
總結(jié)一下,轉(zhuǎn)錄是將構(gòu)建蛋白質(zhì)的遺傳密碼轉(zhuǎn)錄或復(fù)制成信使RNA的過(guò)程·
A gene is a segment of DNA containing the instructions or code for building a protein
基因是DNA的一段區(qū)域,包含構(gòu)建蛋白質(zhì)的指令或編碼·
A codon is a group of three consecutive nitrogenous bases in a gene containing the code for a specific amino acid in a protein
密碼子是基因中由三個(gè)連續(xù)的氮堿基組成的組,包含蛋白質(zhì)中特定氨基酸的編碼·
RNA polymerase unwinds the strands of DNA in a gene
RNA聚合酶解開(kāi)基因中的DNA鏈·
The template DNA strand contains the complementary bases that need to be read to generate messenger RNA
模板DNA鏈包含需要被讀取的互補(bǔ)堿基,以生成信使RNA·
The base pair rule is followed when assembling messenger RNA
在組裝信使RNA時(shí)遵循堿基配對(duì)規(guī)則·
Messenger RNA is actually a copy of the DNA non template strand with uracil substituted for thymine
信使RNA實(shí)際上是DNA非模板鏈的副本,尿嘧啶(U)替代了胸腺嘧啶(T)·