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

진핵 염색체의 DNA 복제는 여러 복제 기원에서 시작되며, 이는 기원 인식 복합체(Origin Recognition Complex, ORC)에 의해 식별되고 결합됩니다.
그런 다음 ORC는 DNA를 풀기 위해 헬리카제를 모집하여 두 개의 복제 분기점이 있는 복제 버블을 생성합니다.
두 갈래는 반대 방향으로 움직이며 앞에 있는 뉴클레오솜을 파괴합니다. 그런 다음 이러한 뉴클레오솜은 딸 가닥에서 재조립되어 염색질 구조를 유지합니다.
각 포크에서 RNA 프라이머는 DNA 중합효소가 선행 가닥과 지연 가닥의 오카자키 단편을 연장할 수 있는 위치를 제공합니다.
그런 다음 RNase 효소가 이러한 프라이머를 제거하고 DNA 중합효소가 그 틈을 채웁니다. 마지막으로, DNA 리가제는 단편을 함께 밀봉합니다.
그러나 선형 염색체 끝의 지연 가닥에서 마지막 프라이머가 제거됨에 따라 템플릿 DNA의 돌출된 스트레치가 생성됩니다.
텔로머라제(telomererase)라고 불리는 효소는 이 돌출된 스트레치를 비코딩 DNA로 확장하여 후속 복제 주기 동안 코딩 DNA의 손실을 방지합니다.
복제는 인접한 복제 버블이 병합되고 전체 염색체가 복제될 때까지 계속됩니다.

진핵생물에서의 복제

진핵 세포에서 DNA 복제는 고도로 보존되고 엄격하게 조절됩니다. 여러 개의 선형 염색체는 세포 분열 전에 높은 정확도로 복제되어야 하므로 복제 과정에서 특수한 역할을 수행하는 단백질이 많이 있습니다. 복제는 개시, 신장, 종료의 세 단계로 이루어지며 핵에서 완전한 두 세트의 염색체로 끝납니다.

많은 단백질이 복제를 근원지에서 조직화합니다

진핵생물 복제는 원핵생물 DNA 복제와 동일한 원리를 많이 따르지만, 게놈이 훨씬 크고 염색체가 원형이 아닌 선형이기 때문에 이 과정에는 더 많은 단백질이 필요하며 몇 가지 주요 차이점이 있습니다. 첫째, 원핵생물과 달리 진핵생물의 복제는 각 염색체를 따라 여러 복제 원점에서 동시에 발생합니다. 개시 단백질은 이러한 기원을 인식하고 결합하며 헬리카제 단백질을 모집하여 DNA 이중 나선을 풀게 됩니다. 각 원본 지점에서 두 개의 복제 포크가 형성됩니다. 그런 다음 Primase는 짧은 RNA 프라이머를 DNA의 단일 가닥에 추가합니다. 이는 DNA 중합효소가 결합하여 서열을 복사하기 시작하는 출발점 역할을 합니다. DNA는 5'에서 3' 방향으로만 합성될 수 있으므로 단일 복제 분기점에서 두 가닥의 복제가 두 가지 다른 방향으로 진행됩니다. 선도 가닥은 연속적으로 합성되는 반면, 지연 가닥은 오카자키 단편이라고 불리는 100-200 염기쌍 길이의 짧은 길이로 합성됩니다. 대량의 복제가 완료되면 RNase 효소가 RNA 프라이머를 제거하고, DNA 중합효소가 틈을 채우고, DNA 리가제가 새로운 가닥의 틈을 밀봉합니다.

중합효소 간 복제 작업 분할

진핵생물에서 DNA를 복사하는 작업량은 다양한 유형의 DNA 중합효소로 나누어집니다. 모든 유기체에 걸친 주요 DNA 중합효소 계열은 단백질 구조와 아미노산 서열의 유사성에 따라 분류됩니다. 처음으로 발견된 과는 A, B, C, X로 명명되었으며 나중에 Y와 D 과로 확인되었습니다. 진핵생물의 계열 B 중합효소에는 복제 분기점에서 프리마제 역할도 하는 Pol α와 각각 주형의 선두 가닥과 지연 가닥에서 DNA 복제 작업의 대부분을 수행하는 효소인 Pol δ 및 ε가 포함됩니다. 다른 DNA 중합효소는 DNA 손상 복구, 미토콘드리아 및 색소체 DNA 복사, RNA 프라이머가 제거된 후 지연 가닥의 DNA 서열 공백 채우기 등의 작업을 담당합니다.

텔로미어는 염색체 말단의 분해를 보호합니다

진핵생물의 염색체는 선형이기 때문에 끝부분이 분해되기 쉽습니다. 중요한 유전 정보를 손상으로부터 보호하기 위해 염색체 말단에는 고도로 보존된 G가 풍부한 DNA의 비암호화 반복인 텔로미어가 많이 포함되어 있습니다. 염색체의 각 끝에 있는 짧은 단일 가닥 3' 돌출부는 특수 단백질과 상호 작용하여 핵 내에서 염색체를 안정화시킵니다. 지연 가닥이 합성되는 방식으로 인해 각 세포 분열에서 소량의 텔로미어 DNA가 복제될 수 없습니다. 결과적으로, 텔로미어는 많은 세포 주기가 진행되는 동안 점점 짧아져 세포 노화의 지표로 측정될 수 있습니다. 생식 세포 및 줄기 세포와 같은 특정 세포 집단은 텔로미어를 늘리는 효소인 텔로머라제를 발현하여 텔로미어가 짧아지기 전에 세포가 더 많은 세포 주기를 겪도록 합니다.

진핵 세포에서 DNA 복제는 고도로 보존되고 엄격하게 조절됩니다. 여러 선형 염색체는 이전에 높은 충실도로 복제되어야 합니다.

Education

교육

JoVE Core

Anatomy and Physiology

해부학 및 생리학

Unit 1

제1단원

Essential Cellular Processes

필수 세포 과정

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 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

Regulation of Expression at Multiple Steps

The gene expression in cells is regulated at different stages: (i) transcription, (ii) RNA processing, (iii) RNA localization, and (iv) translation. ...

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

The ability of a drug to produce structural deformations and functional abnormalities in the developing embryo or the fetus is called teratogenicity, and ...

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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