Name: eukaryotic dna copying at the replication fork
Uploaded: 2023-06-23T15:38:45.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Georgia Standards of Excellence

9-12

Biology

SB2.a

Replication in Eukaryotes

真核生物染色体中的DNA复制起始于多个复制起点，这些复制起点由复制起点识别复合物（ORC）识别并结合。
ORC 随后招募解旋酶以解开 DNA，形成一个具有两个复制叉的复制泡。
两个复制叉朝相反方向移动，并解聚其前方的核小体。这些核小体随后在子代链上重新组装，从而维持染色质结构。
在每个复制叉处，RNA 引物为 DNA 聚合酶提供作用位点，以延伸前导链和后随链上的冈崎片段。
随后，RNase酶会切除这些引物，DNA聚合酶填补缺口，最后由DNA连接酶将片段连接在一起。
然而，当线性染色体末端的滞后链上最后一个引物被移除后，会产生一段突出的模板DNA。
一种称为端粒酶的酶通过添加非编码DNA来延伸这一突出的末端，从而防止在后续复制周期中编码DNA的丢失。 
复制持续进行，直到相邻的复制泡合并，整个染色体被复制完成。

真核生物中的复制

在真核细胞中，DNA复制是一个高度保守且受到严格调控的过程。在细胞分裂之前，必须以高保真度复制多个线性染色体，因此有许多蛋白质在复制过程中发挥特殊作用。复制分为起始、延伸和终止三个阶段，最终结果是细胞核内形成两套完整的染色体。

许多蛋白质在复制起点协同作用

真核生物的DNA复制遵循许多与原核生物DNA复制相同的原理，但由于基因组更大且染色体是线性的而非环形的，因此该过程需要更多的蛋白质，并且有一些关键的差异。首先，与原核生物不同，真核生物的复制沿着每条染色体在多个复制起点同时进行。起始蛋白识别并结合这些复制起点，并招募解旋酶蛋白来解开 DNA 双螺旋。在每个起始点，都会形成两个复制叉。然后引物酶将短 RNA 引物添加到 DNA 单链上，作为 DNA 聚合酶结合并开始复制序列的起点。DNA 只能以 5' 至 3' 方向合成，因此来自单个复制叉的两条链的复制以两个不同的方向进行。前导链是连续合成的，而后随链则以100-200个碱基对的短片段合成，称为冈崎片段。一旦大部分复制完成，RNase 酶就会去除 RNA 引物，DNA 聚合酶会填充间隙，DNA 连接酶会密封新链中的间隙。

DNA聚合酶分担复制工作

在真核生物中，复制DNA的工作由多种不同类型的DNA聚合酶酶分担。所有生物体中 DNA 聚合酶的主要家族根据其蛋白质结构和氨基酸序列的相似性进行分类。第一批被发现的家族被称为 A、B、C 和 X，随后又确定了 Y 和 D 家族。真核生物中的 B 族聚合酶包括 Pol α（也可作为复制叉处的引物酶）以及 Pol δ 和 ε（分别在模板的前导链和后随链上完成 DNA 复制的大部分工作）。其他 DNA 聚合酶负责修复 DNA 损伤、复制线粒体和质体 DNA 以及在 RNA 引物被去除后填充后随链上 DNA 序列的间隙。

端粒保护染色体末端免遭降解

由于真核染色体是线性的，它们的末端很容易降解。为了保护重要的遗传信息免受损害，染色体的末端包含许多非编码的、高度保守的富含G的DNA重复序列，即端粒。染色体两端的短单链 3' 突出端与特殊蛋白质相互作用，从而稳定细胞核内的染色体。由于后随链的合成方式，每次细胞分裂时都有一小部分端粒DNA无法复制。因此，在多个细胞周期的过程中，端粒会逐渐变短，因此可以作为细胞衰老的标志物。某些细胞群，例如生殖细胞和干细胞，表达端粒酶，这是一种延长端粒的酶，使细胞在端粒缩短之前经历更多的细胞周期。

在真核细胞中，DNA复制具有高度保守性且受到严格调控。多条线性染色体必须在...

Education

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JoVE Core

Anatomy and Physiology

解剖学与生理学

Unit 1

第 1 单元

Essential Cellular Processes

细胞基本过程

KEY TERMS AND CONCEPTS

关键术语与概念

eukaryotic dna copying at the replication fork

Eukaryotic DNA copying happens at replication forks, where the two DNA strands separate and new strands are built. This process lets a cell make an exact copy of its genetic material before it divides.

The transcript explains that eukaryotic replication follows the same basic steps seen in other DNA replication systems, but it takes place in cells with a nucleus. The replication machinery works on each separated strand as a template, so the new DNA matches the original sequence.

This topic is important for high school biology because it connects DNA structure to cell division and inheritance. Understanding replication in eukaryotes helps students see how genetic information is passed on when body cells grow and reproduce.

Eukaryotic DNA Copying at the Replication Fork

eukaryotic-dna-copying-at-the-replication-fork

the central dogma

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The central dogma explains how genetic information flows in cells from DNA to RNA to protein. It is a core idea in molecular biology and helps show how genes influence cell function. DNA stores the instructions. During transcription, a cell copies a gene into RNA, which is a related nucleic acid. That RNA message can then be used in translation to build a protein. Proteins carry out many jobs in cells and help determine traits. The central dogma links the genetic code in DNA to the molecules...

replication in eukaryotes

Eukaryotic DNA copying happens at replication forks, where the two DNA strands separate and new strands are built. This process lets a cell make an exact copy of its genetic material before it divides. The transcript explains that eukaryotic replication follows the same basic steps seen in other DNA replication systems, but it takes place in cells with a nucleus. The replication machinery works on each separated strand as a template, so the new DNA matches the original sequence. This topic is...

types of rna

RNA Types in Gene Expression

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interphase

Interphase and Cell Growth

Interphase is the part of the cell cycle when a cell grows and prepares to divide. It is a major stage of the cell cycle, and it comes before cell division begins. During interphase, the cell carries out its normal functions. It also copies its DNA so each new cell can receive a full set of genetic material. The cell may also build up the materials it needs for division. Interphase is not a single step. It includes phases such as G1, S, and G2, which help the cell grow, copy DNA, and get...

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the cell cycle control system

Cell Cycle Checkpoints and Cyclin Control

The cell cycle is controlled by checkpoints that help a cell move from one phase to the next and begin mitosis. This control system uses internal regulatory molecules and outside signals to send stop or advance instructions. It makes sure each step is finished before the cell moves forward. Cyclins and cyclin-dependent kinases, or Cdks, are the main regulators of the cell cycle. They act during the G1, G2, and M phases. These regulators work at specific checkpoints to keep cell division...

molecular factors affecting cell division

molecular-factors-affecting-cell-division

Cell Cycle Regulators That Control Division

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what is meiosis?

Meiosis and the Formation of Gametes

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overview of cell signaling

Cell Signaling Pathways and Responses

Cell signaling pathways and responses help cells communicate and react to changes. Cells send signals to one another, and those signals can trigger a specific response in the target cell. A signal usually begins when a signaling molecule reaches a cell with the right receptor, which is a protein that receives the message. The receptor helps the cell recognize the signal and start the communication process. Inside the cell, the message can move through a signaling pathway. This pathway passes...

types of signaling molecules

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g protein-coupled receptors

G Protein-coupled Receptor Signaling

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cellular differentiation

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Cellular differentiation turns unspecialized cells into specialized cells with specific jobs. This process helps a complex organism, such as a human, develop from a single fertilized egg into a body with many cell types. Nerve cells, muscle cells, and epithelial cells are examples of the final cell types that appear during development. A zygote is the first cell after fertilization. It is a totipotent stem cell, which means it has very high differentiation potential and can form all cell types...

key terms and concepts

Learn how eukaryotic DNA is copied at replication forks, where strands separate and new DNA is built before cell division in nucleus-containing cells.

Eukaryotic DNA Copying at the Replication Fork | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

The Central Dogma

Types of RNA

Transcription

Translation

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Construct an explanation of how the structures of DNA and RNA lead to the expression of information within the cell via the processes of replication, transcription, and translation

What is Meiosis?

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Meiosis II

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SB2.b

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SB2.c

Obtain, evaluate, and communicate information to analyze how genetic information is expressed in cells

Eukaryotic DNA Copying at the Replication Fork

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