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

Replikacja DNA w chromosomach eukariotycznych rozpoczyna się w wielu początkach replikacji, które są identyfikowane i wiązane przez kompleks rozpoznawania pochodzenia lub ORC.
Następnie ORC rekrutuje helikazy do rozwijania DNA, wytwarzając pęcherzyk replikacyjny z dwoma widełkami replikacyjnymi.
Dwa widełki poruszają się w przeciwnych kierunkach i rozrywają nukleosomy przed nimi. Te nukleosomy są następnie ponownie składane na niciach potomnych, utrzymując strukturę chromatyny.
Na każdym rozwidleniu startery RNA zapewniają miejsce dla polimerazy DNA w celu wydłużenia nici wiodącej i fragmentów Okazaki nici opóźnionej.
Enzym RNaza następnie usuwa te startery, a polimeraza DNA wypełnia luki. Wreszcie ligaza DNA uszczelnia fragmenty razem.
Jednakże, gdy ostatni starter jest usuwany z opóźnionej nici na końcu chromosomu liniowego, wytwarza zwisający odcinek matrycowego DNA.
Enzym zwany telomerazą rozszerza ten zwisający odcinek za pomocą niekodującego DNA, aby zapobiec utracie kodującego DNA podczas kolejnych cykli replikacji.
Replikacja trwa do momentu, gdy sąsiednie pęcherzyki replikacyjne połączą się i cały chromosom zostanie zduplikowany.

replikacja u eukariontów

W komórkach eukariotycznych replikacja DNA jest wysoce konserwatywna i ściśle regulowana. Wiele chromosomów liniowych musi zostać zduplikowanych z dużą wiernością przed podziałem komórki, dlatego istnieje wiele białek, które spełniają wyspecjalizowane role w procesie replikacji. Replikacja przebiega w trzech fazach: inicjacji, elongacji i terminacji i kończy się dwoma kompletnymi zestawami chromosomów w jądrze. Wiele białek organizuje replikację w miejscu pochodzenia Replikacja eukariotyczna opiera się na wielu tych samych zasadach, co replikacja DNA prokariotycznego, ale ponieważ genom jest znacznie większy, a chromosomy są raczej liniowe niż kołowe, proces ten wymaga większej ilości białek i ma kilka kluczowych różnic. Po pierwsze, w przeciwieństwie do prokariotów, replikacja u eukariontów zachodzi jednocześnie w wielu miejscach początku replikacji wzdłuż każdego chromosomu. Białka inicjujące rozpoznają i wiążą się z tymi miejscami początkowymi oraz rekrutują białka helikazy do rozwinięcia podwójnej helisy DNA. W każdym punkcie początkowym tworzą się dwa widełki replikacyjne. Następnie prymasa dodaje krótkie startery RNA do pojedynczych nici DNA, które służą jako punkt wyjścia dla polimerazy DNA do wiązania się i rozpoczęcia kopiowania sekwencji. DNA można syntetyzować tylko w kierunku od 5' do 3', zatem replikacja obu nici z pojedynczego widełka replikacyjnego przebiega w dwóch różnych kierunkach. Nić wiodąca jest syntetyzowana w sposób ciągły, podczas gdy nić opóźniona jest syntetyzowana w krótkich odcinkach o długości 100–200 par zasad, zwanych fragmentami Okazaki. Po zakończeniu większości replikacji enzymy RNazy usuwają startery RNA, polimeraza DNA wypełnia luki, a ligaza DNA uszczelnia luki w nowej nici. Podział pracy replikacji wśród polimeraz Nakład pracy związany z kopiowaniem DNA u eukariontów jest podzielony pomiędzy wiele różnych typów enzymów polimerazy DNA. Główne rodziny polimeraz DNA we wszystkich organizmach są klasyfikowane na podstawie podobieństwa ich struktur białkowych i sekwencji aminokwasów. Pierwsze odkryte rodziny nazwano A, B, C i X, a rodziny Y i D zidentyfikowano później. Polimerazy z rodziny B u eukariontów obejmują Pol α, która działa również jako prymaza w widełkach replikacyjnych, oraz Pol δ i ε, enzymy, które wykonują większość pracy związanej z replikacją DNA, odpowiednio na nici wiodącej i opóźnionej matrycy. Inne polimerazy DNA odpowiadają za takie zadania, jak naprawa uszkodzeń DNA, kopiowanie mitochondrialnego i plastydowego DNA oraz wypełnianie luk w sekwencji DNA na nici opóźnionej po usunięciu starterów RNA. Telomery chronią końce chromosomów przed degradacją Ponieważ chromosomy eukariotyczne są liniowe, są podatne na degradację na końcach. Aby chronić ważną informację genetyczną przed uszkodzeniem, końce chromosomów zawierają wiele niekodujących powtórzeń wysoce konserwatywnego DNA bogatego w G, czyli telomerów. Krótki jednoniciowy zwis 3' na każdym końcu chromosomu oddziałuje z wyspecjalizowanymi białkami, które stabilizują chromosom w jądrze. Ze względu na sposób syntezy nici opóźnionej niewielka ilość telomerowego DNA nie może być replikowana podczas każdego podziału komórki. W rezultacie telomery stopniowo ulegają skróceniu w trakcie wielu cykli komórkowych, co można zmierzyć jako marker starzenia się komórek. Niektóre populacje komórek, takie jak komórki rozrodcze i komórki macierzyste, wykazują ekspresję telomerazy – enzymu, który wydłuża telomery, umożliwiając komórce przejście większej liczby cykli komórkowych, zanim telomery się skrócą.

Replikacja u eukariontów

W komórkach eukariotycznych replikacja DNA jest wysoce konserwatywna i ściśle regulowana. Wiele chromosomów liniowych musi zostać zduplikowanych z wysoką wiernością przed ...

Education

JoVE Core

Anatomy and Physiology

Anatomia i fizjologia

Unit 1

Jednostka 1

Essential Cellular Processes

Podstawowe procesy komórkowe

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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

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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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transcription

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translation

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regulation of expression at multiple steps

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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

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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

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

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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

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Meiosis II

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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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