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

DNA復制是指原始DNA分子解鏈并通過堿基互補配對原則形成兩個子DNA鏈的生物學過程，該過程發生在細胞分裂周期的S期。DNA復制以親代DNA分子為模板，脫氧核苷三磷酸為底物，還需相關酶和蛋白因子的參與，如：DNA聚合酶、DNA引物酶、DNA連接酶、核酸外切酶、拓撲異構酶、引發體等。

DNA復制過程包括引發、延伸、終止三個階段，DNA雙鏈在復制起點的解旋酶作用下形成單鏈模板，從RNA引物的3’-OH末端開始，沿5’→3’方向連續不斷地添加堿基，再通過共價連接成一條連續完整的新DNA鏈。

DNA復制具有半保留復制、雙向復制、半不連續復制等特點，1953年James Watson和Francis Crick提出DNA雙螺旋結構后，1958年Meselson-Stahl實驗通過氮同位素標記證實了DNA的半保留復制機制。

DNA復制是生命體最基礎的生物學過程，控制著遺傳信息的精確和穩定傳遞，是生物遺傳的基礎，為生命的演化提供了根基。通過對DNA復制的機制的研究，可以深入了解DNA復制在疾病發生發展中的作用，從而為疾病的診斷、治療和預防提供依據。例如，DNA復制錯誤可能引發突變，導致遺傳性疾病的發生，如21-三體綜合征、先天性的耳聾、色盲、血友病、白化病等。

內容操作
視頻
教程課件
單詞卡片
Let's take a look at DNA replication the process in which DNA copies itself
讓我們來看一下DNA復制,DNA自我復制的過程·
Why does DNA need to copy itself
為什么DNA需要復制自己?
Well before a cell divides during mitosis it must make a copy of its original DNA
嗯,在有絲分裂期間,細胞在分裂之前必須復制其原始DNA·
This ensures that both resulting daughter cells will have DNA that is identical to the original cell's DNA
這確保了兩個子細胞將擁有與原始細胞DNA完全相同的DNA·
So at what point in the cell cycle does DNA replication happen
那么,DNA復制發生在細胞周期的哪個階段?
DNA is copied or replicated during the S phase of the cell cycle
DNA在細胞周期的S期復制或復制·
A good way to remember this is that S stands for synthesis which means to make
記住這一點的好方法是,S代表合成(synthesis),意思是"制造"·
Now let's see how DNA replicates during the S phase
現在,讓我們看看DNA在S期是如何復制的·
If we zoom into the nucleus we can see the DNA molecules two strands or sides twisted together in the classic double helix formation
如果我們放大到細胞核內,我們可以看到DNA分子呈經典的雙螺旋結構,兩個鏈或兩邊相互纏繞·
The two strands are connected by hydrogen bonds between their nitrogenous bases
這兩條鏈通過它們的氮堿基之間的氫鍵連接在一起·
The first step of replication begins with an enzyme called DNA helicase
復制的第一步是由一種叫做DNA解旋酶(DNA helicase)的酶開始的·
The suffix A S E or ASE tells you right away that helicase is an enzyme
后綴A-S-E或ASE表明解旋酶是一種酶·
Helicase unwinds and then separates the two sides of the DNA molecule by breaking the hydrogen bonds between their nitrogenous bases
解旋酶通過打破氮堿基之間的氫鍵,解開并分開DNA分子的兩條鏈·
Each separate half of the DNA can now serve as a template or pattern for the creation of a new strand of DNA
DNA的每一半現在都可以作為模板或圖案,用于創建新的DNA鏈·
This separation exposes all of the nitrogenous bases on both sides of the DNA to the environment within the nucleus where free nucleotides are present
這種分離使DNA兩側的所有氮堿基暴露在細胞核內的環境中,在那里自由核苷酸存在·
This brings us to the second step in DNA replication the creation of two new identical DNA strands
這就引出了DNA復制的第二步,即創建兩個新的相同的DNA鏈·
An enzyme that assists in this process is called DNA polymerase
在這個過程中起作用的酶叫做DNA聚合酶(DNA polymerase)·
It adds free nucleotides available in the nucleus to the original template strands
它將細胞核中可用的自由核苷酸添加到原始模板鏈上·
DNA polymerase does this by creating new hydrogen bonds between the available nitrogenous bases of the free nucleotides and those on both sides of the original DNA molecule
DNA聚合酶通過在自由核苷酸的氮堿基和原始DNA分子兩側的氮堿基之間形成新的氫鍵來完成這個過程·
New nucleotides are added to the template strands following the base pair rule of nitrogenous bases
新的核苷酸被添加到模板鏈上,遵循氮堿基的配對規則·
Remember in DNA adenine always bonds with thymine
記住,在DNA中,腺嘌呤(A)總是與胸腺嘧啶(T)配對·
Thymine always bonds with adenine
胸腺嘧啶(T)總是與腺嘌呤(A)配對·
Guanine always bonds with cytosine
鳥嘌呤(G)總是與胞嘧啶(C)配對,
and cytosine always bonds with guanine
而胞嘧啶(C)總是與鳥嘌呤(G)配對·
So these newly attached nucleotides form a mirror image or complementary strand on each template strand of the original DNA
因此,這些新附著的核苷酸在原始DNA的每個模板鏈上形成了鏡像或互補鏈·
As a result of this replication process two duplicate molecules of DNA are produced from the original DNA molecule
由于這個復制過程,兩個DNA的副本分子從原始DNA分子中產生·
With DNA replication now completed the cell is ready to begin mitosis
DNA復制現在已經完成,細胞準備開始有絲分裂·
We will cover mitosis in another video
我們將在另一段視頻中講解有絲分裂·
In summary DNA replication is a process in which DNA duplicates itself making an identical copy
總之,DNA復制是DNA自我復制的過程,生成一個相同的副本·
Replication occurs during the S phase of the cell cycle when a somatic cell is preparing to divide
復制發生在細胞周期的S期,當一個體細胞準備分裂時·
DNA replication is necessary so that the two daughter cells produced after mitosis both have DNA that is identical to each other and identical to the DNA in the original cell
DNA復制是必要的,這樣在有絲分裂后生成的兩個子細胞才能擁有相同的DNA,并且與原始細胞的DNA完全相同·
At the beginning of replication an enzyme called DNA helicase breaks the hydrogen bonds between nitrogenous bases and unwinds the DNA molecule
在復制的開始,一種叫做DNA解旋酶的酶會打破氮堿基之間的氫鍵,并解開DNA分子·
Each side of the original DNA molecule serves as a template for the creation of a new complementary strand of DNA
原始DNA分子的每一側作為模板,用于創建新的互補DNA鏈·
With the assistance of DNA polymerase and other enzymes
在DNA聚合酶和其他酶的幫助下,
free nucleotides are added to the template strands following the base pair rule
遵循氮堿基配對規則,將自由核苷酸添加到模板鏈上·
The result of DNA replication is two identical duplicate DNA molecules from the original DNA molecule
DNA復制的結果是從原始DNA分子中生成兩個相同的DNA副本·