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

真核生物の染色体におけるDNA複製は、複数の複製起点で開始され、それらは起源認識複合体(ORC)によって同定され、結合されます。
次に、ORCはヘリカーゼをリクルートしてDNAを巻き戻し、2つの複製フォークで複製バブルを生成します。
2つのフォークは反対方向に動き、前方のヌクレオソームを破壊します。その後、これらのヌクレオソームは娘鎖上で再集合し、クロマチン構造を維持します。
各フォークでは、RNAプライマーがDNAポリメラーゼの部位を提供し、遅延鎖の先頭鎖と岡崎断片を伸長させます。
次に、RNase酵素がこれらのプライマーを除去し、DNAポリメラーゼがギャップを埋めます。最後に、DNAリガーゼがフラグメントを一緒にシールします。
しかし、最後のプライマーが線状染色体の末端にある遅行鎖から取り除かれると、テンプレートDNAの張り出したストレッチが生成されます。
テロメラーゼと呼ばれる酵素は、この張り出したストレッチをノンコーディングDNAで拡張し、その後の複製サイクルでコーディングDNAが失われるのを防ぎます。
複製は、隣接する複製バブルが結合し、染色体全体が複製されるまで続きます。

真核生物でのレプリケーション

真核細胞では、DNA 複製は高度に保存され、厳密に調節されています。 細胞分裂の前に複数の直鎖状染色体を高い忠実度で複製する必要があるため、複製プロセスで特殊な役割を果たすタンパク質が多数存在します。 複製は開始、伸長、および終了の 3 つの期で起こり、核内の 2 つの完全な染色体をセットして終了します。

多くのタンパク質が起点で複製を調整する

真核生物の複製は、原核生物の DNA 複製と同じ原理の多くに従いますが、ゲノムがはるかに大きく、染色体が環状ではなく線状であるため、そのプロセスにはより多くのタンパク質が必要となり、いくつかの重要な違いがあります。 まず、原核生物とは異なり、真核生物の複製は各染色体に沿った複数の複製起点で同時に起こります。 イニシエータータンパク質はこれらの起点を認識して結合し、ヘリカーゼタンパク質を動員して DNA 二重らせんを巻き戻します。 各起点で 2 つのレプリケーション フォークが形成されます。 次に、プライマーゼは短い RNA プライマーを DNA の一本鎖に追加します。これは、DNA ポリメラーゼが結合して配列のコピーを開始する開始点として機能します。 DNA は 5' から 3' 方向にのみ合成できるため、1 つの複製フォークからの両方の鎖の複製は 2 つの異なる方向に進行します。 リーディング鎖は連続的に合成されますが、ラギング鎖は岡崎フラグメントと呼ばれる長さ 100 ～ 200 塩基対の短いストレッチで合成されます。 複製の大部分が完了すると、RNase 酵素が RNA プライマーを除去し、DNA ポリメラーゼがギャップを埋め、DNA リガーゼが新しい鎖のギャップをシールします。

複製の仕事をポリメラーゼ間で分割する

真核生物における DNA コピーの作業負荷は、複数の異なる種類の DNA ポリメラーゼ酵素に分割されます。 すべての生物の DNA ポリメラーゼの主要なファミリーは、タンパク質構造とアミノ酸配列の類似性によって分類されます。 最初に発見されたファミリーは A、B、C、X と名付けられ、後にファミリー Y と D が特定されました。 真核生物のファミリー B ポリメラーゼには、複製フォークでプライマーゼとしても機能する Pol α と、それぞれ鋳型のリーディング鎖とラギング鎖で DNA 複製の仕事のほとんどを行う酵素である Pol δ と ε が含まれます。 他の DNA ポリメラーゼは、DNA 損傷の修復、ミトコンドリアおよび色素体 DNA のコピー、RNA プライマーが除去された後のラギング鎖上の DNA 配列のギャップを埋めるなどの役割を担っています。

テロメアは染色体の末端を劣化から保護します

真核生物の染色体は線状であるため、末端が分解されやすいです。 重要な遺伝情報を損傷から守るために、染色体の末端には、高度に保存された G リッチ DNA の非コード反復であるテロメアが多数含まれています。 染色体の両端にある短い一本鎖の3' オーバーハングは特殊なタンパク質と相互作用し、核内の染色体を安定化します。 ラギング鎖の合成方法により、細胞分裂のたびに少量のテロメア DNA が複製できなくなります。 その結果、多くの細胞周期の過程でテロメアが徐々に短くなり、細胞の老化のマーカーとして測定できるようになります。 生殖細胞や幹細胞などの特定の細胞集団は、テロメアを延長する酵素であるテロメラーゼを発現し、テロメアが短くなる前に細胞がより多くの細胞周期を行えるようにします。

真核細胞では、DNA複製は高度に保存され、厳密に制御されています。複数の線状染色体を高い忠実度で複製する必要があります...

Education

JoVE Core

Anatomy and Physiology

解剖生理学

Unit 1

ユニット1

Essential Cellular Processes

細胞の基本的プロセス

KEY TERMS AND CONCEPTS

主要用語と概念

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

Central Dogma: DNA to Protein

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

RNA types play different roles in gene expression. RNA, or ribonucleic acid, helps carry and use genetic information in cells. The main types discussed here are messenger RNA, ribosomal RNA, and transfer RNA. Messenger RNA, or mRNA, carries the genetic code from DNA to the ribosome. The ribosome is the site where proteins are made. Ribosomal RNA, or rRNA, is a key part of the ribosome itself. Transfer RNA, or tRNA, brings the correct amino acids to the ribosome during protein building. These...

transcription

Transcription and RNA Synthesis

Transcription is the process of making RNA from a DNA template. It is a key step in gene expression, because cells use the DNA sequence to build an RNA copy that can carry the message forward. During transcription, RNA polymerase binds to DNA and reads one strand as the template. The enzyme links RNA nucleotides together in the correct order to form a growing RNA molecule. This copying step does not make DNA; it produces RNA. The transcript focuses on the central idea of transcription as DNA...

translation

Translation: mRNA to Protein

Translation is the step in gene expression where ribosomes use messenger RNA, or mRNA, to build a protein. The mRNA sequence carries the instructions copied from DNA. During translation, those instructions are read in order so the cell can make a specific chain of amino acids. This process depends on the ribosome and transfer RNA, or tRNA. The ribosome reads the mRNA, and tRNA brings the matching amino acids. As the chain grows, the amino acids are linked together to form a polypeptide, which...

regulation of expression at multiple steps

regulation-of-expression-at-multiple-steps

How Cells Control Gene Expression

Cells control gene expression at several stages, from making RNA to building protein. These checkpoints include transcription, RNA processing, RNA localization, and translation. Together, they help decide when a gene is used and whether a protein is made. Transcription is controlled by regulatory proteins. Transcription factors, activators, and repressors can start or slow the transcription of genes. After transcription, the cell makes a precursor RNA, also called pre-mRNA. Pre-mRNA must be...

what is the cell cycle?

Cell Cycle Stages in Cell Growth

The cell cycle is the process that controls cell growth and division. It explains how one cell makes two new cells. This process helps cells grow and reproduce.

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...

mitosis and cytokinesis

Cell Division: Mitosis and Cytokinesis

Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells. These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells...

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

Cell division is controlled by outside signals and by internal cell cycle regulators. Nearby cell death can encourage division, and human growth hormone (hGH) can also promote it. In contrast, too little hGH or crowded cells can slow or stop division. Inside the cell, regulator molecules help each stage finish correctly before the next stage begins. Some regulators act directly on the cycle, while others affect the activity or production of other regulatory proteins. These molecules can either...

what is meiosis?

Meiosis and the Formation of Gametes

Meiosis is the cell division process that forms gametes, or sex cells. It reduces the chromosome number so offspring can inherit the correct amount of genetic material. This process includes two successive divisions. First, one cell divides, and then the resulting cells divide again. These steps separate the genetic material in a controlled way. Meiosis helps explain how sexual reproduction passes traits from one generation to the next. It is a key topic in high school biology because it...

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

Chemical Messengers in Cell Signaling

Chemical messengers help cells communicate during signaling. These signaling molecules carry information from one cell to another and guide how cells respond. Some signaling molecules are gases, while others are proteins or peptides. Small lipids can also act as signals. In addition, cells may use steroids, amino acids, and even ions as signaling molecules. Each type of signaling molecule has different properties and works in a different way. Together, these molecules let cells send specific...

g protein-coupled receptors

G Protein-coupled Receptor Signaling

G protein-coupled receptors are a major class of cell-surface receptors. They help cells detect signals outside the cell and pass that information inward. These receptors are important in many kinds of cell communication. When a signal binds to a G protein-coupled receptor, the receptor changes shape. That change activates a G protein inside the cell. The activated G protein can then start a signaling pathway. This signaling system includes the receptor, the G protein, and the downstream...

cellular differentiation

From Stem Cell to Specialized Cells

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 解剖学と生理学では、人体の解剖学的および生理学的な詳細を、包括的で明確で魅力的なビデオ アニメーションで紹介します。このレッスン集は、人体の構造、コンポーネント、機能、要件に焦点を当てています。この知識を実際の医療および研究現場で応用することを実証する科学者による実際のビデオによって補完されています。

The Central Dogma

Types of RNA

Transcription

Translation

Regulation of Expression at Multiple Steps

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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?

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of ...

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for ...

Crossing over

Nondisjunction

Genome Copying Errors

DNA replication is a well-evolved process that copies millions of base pairs with high fidelity during each cell division. Occasionally a wrong base or a ...

Overview of DNA Repair

In order to be passed through generations, genomic DNA must be undamaged and error-free. However, every day, DNA in a cell undergoes several thousand to a ...

Base Excision Repair

One of the common DNA damages is the chemical alteration of single bases by alkylation, oxidation, or deamination. The altered bases cause mispairing and ...

RNA Editing

RNA editing is a post-transcriptional modification where a precursor mRNA (pre-mRNA) nucleotide sequence is changed by base insertion, deletion, or ...

Mutations

Teratogenicity

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Mechanisms of Retrovirus-induced Cancers

Retroviruses are RNA viruses that have been shown to cause cancers in diverse species, including chickens, mice, cats, and monkeys. The RNA genomes of ...

Construct an argument based on evidence to support the claim that inheritable genetic variations may result from:New genetic combinations through meiosis (crossing over, nondisjunction), Non-lethal errors occurring during replication (insertions, deletions, substitutions), Heritable mutations caused by environmental factors (radiation, chemicals, and viruses)

SB2.b

Transgenic Plants

Recombinant DNA technology called transgenesis is often used to add a foreign gene or remove a detrimental gene from an organism. Such genetically ...

Transgenic Organisms

Overview

Transgenic organisms are genetically engineered to carry transgenes&#x2014;genes from a different species&#x2014;as part of their genome. The ...

Testing For Genetically Modified Foods

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Genetic modification of foods has been a controversial issue due to debated ...

Genetic Engineering of Model Organisms

Transgenesis, or the use of genetic engineering to alter gene expression, is widely used in the field of developmental biology. Scientists use a number of ...

Ask questions to gather and communicate information about the use and ethical considerations of biotechnology in forensics, medicine, and agriculture

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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