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

A replicação do DNA em cromossomos eucarióticos inicia-se em múltiplas origens de replicação, que são identificadas e ligadas pelo complexo de reconhecimento de origem, ou ORC.
O ORC então recruta helicases para desenrolar o DNA, produzindo uma bolha de replicação com dois garfos de replicação.
As duas bifurcações se movem em direções opostas e interrompem os nucleossomos à sua frente. Esses nucleossomos são então remontados nas fitas filhas, mantendo a estrutura da cromatina.
Em cada bifurcação, os primers de RNA fornecem o local para a DNA polimerase alongar a fita principal e os fragmentos de Okazaki da fita atrasada.
Uma enzima RNase remove esses primers e a DNA polimerase preenche as lacunas. Finalmente, a DNA ligase sela os fragmentos.
No entanto, à medida que o último primer é removido da fita atrasada no final do cromossomo linear, ele produz um trecho saliente do DNA molde.
Uma enzima chamada telomerase estende esse trecho saliente com DNA não codificante para evitar a perda de DNA codificante durante os ciclos de replicação subsequentes.
A replicação continua até que as bolhas de replicação adjacentes se fundam e todo o cromossomo seja duplicado.

replicação em eucariotos

Nas células eucarióticas, a replicação do DNA é altamente conservada e fortemente regulada. Múltiplos cromossomos lineares devem ser duplicados com alta fidelidade antes da divisão celular, portanto, existem muitas proteínas que desempenham funções especializadas no processo de replicação. A replicação ocorre em três fases: iniciação, alongamento e terminação, e termina com dois conjuntos completos de cromossomos no núcleo. Muitas Proteínas Orquestram a Replicação na Origem A replicação eucariótica segue muitos dos mesmos princípios da replicação do DNA procariótico, mas como o genoma é muito maior e os cromossomos são lineares em vez de circulares, o processo requer mais proteínas e tem algumas diferenças importantes. Primeiro, ao contrário dos procariontes, a replicação nos eucariotos ocorre simultaneamente em múltiplas origens de replicação ao longo de cada cromossomo. As proteínas iniciadoras reconhecem e ligam-se a essas origens e recrutam proteínas helicase para desenrolar a dupla hélice do DNA. Em cada ponto de origem, formam-se duas forquilhas de replicação. A primase então adiciona primers curtos de RNA às fitas simples de DNA, que servem como ponto de partida para a DNA polimerase se ligar e começar a copiar a sequência. O DNA só pode ser sintetizado na direção 5' para 3', portanto a replicação de ambas as fitas de uma única forquilha de replicação ocorre em duas direções diferentes. A fita principal é sintetizada continuamente, enquanto a fita atrasada é sintetizada em trechos curtos de 100 a 200 pares de bases de comprimento, chamados fragmentos de Okazaki. Uma vez concluída a maior parte da replicação, as enzimas RNase removem os iniciadores de RNA, a DNA polimerase preenche as lacunas e a DNA ligase sela as lacunas na nova fita. Dividindo o Trabalho de Replicação entre Polimerases A carga de trabalho da cópia do DNA em eucariotos é dividida entre vários tipos diferentes de enzimas DNA polimerase. As principais famílias de DNA polimerases em todos os organismos são categorizadas pela semelhança de suas estruturas proteicas e sequências de aminoácidos. As primeiras famílias a serem descobertas foram denominadas A, B, C e X, com as famílias Y e D identificadas posteriormente. As polimerases da família B em eucariotos incluem Pol α, que também funciona como primase na forquilha de replicação, e Pol δ e ε, as enzimas que fazem a maior parte do trabalho de replicação do DNA nas fitas principal e atrasada do modelo, respectivamente. Outras DNA polimerases são responsáveis por tarefas como reparar danos no DNA, copiar DNA mitocondrial e plastidial e preencher lacunas na sequência de DNA na fita retardada após a remoção dos primers de RNA. Os Telômeros Protegem as Extremidades dos Cromossomos da Degradação Como os cromossomos eucarióticos são lineares, eles são suscetíveis à degradação nas extremidades. Para proteger informações genéticas importantes contra danos, as extremidades dos cromossomos contêm muitas repetições não codificantes de DNA rico em G altamente conservado, os telômeros. Uma curta saliência 3' de fita simples em cada extremidade do cromossomo interage com proteínas especializadas, que estabilizam o cromossomo dentro do núcleo. Devido à maneira como a fita retardada é sintetizada, uma pequena quantidade do DNA telomérico não pode ser replicada em cada divisão celular. Como resultado, os telômeros ficam gradualmente mais curtos ao longo de muitos ciclos celulares e, portanto, podem ser medidos como um marcador do envelhecimento celular. Certas populações de células, como células germinativas e células-tronco, expressam telomerase, uma enzima que alonga os telômeros, permitindo que a célula passe por mais ciclos celulares antes que os telômeros encurtem.

Replicação em Eucariotos

Em células eucarióticas, a replicação do DNA é altamente conservada e rigidamente regulada. Vários cromossomos lineares devem ser duplicados com alta fidelidade antes de ...

Education

JoVE Core

Anatomy and Physiology

Anatomia e Fisiologia

Unit 1

Unidade 1

Essential Cellular Processes

Processos Celulares Essenciais

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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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transcription

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regulation of expression at multiple steps

regulation-of-expression-at-multiple-steps

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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...

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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...

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Chemical Messengers in Cell Signaling

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g protein-coupled receptors

G Protein-coupled Receptor Signaling

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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

O JoVE Core Anatomia e Fisiologia apresenta detalhes anatômicos e fisiológicos do corpo humano em animações  abrangentes, claras e envolventes. Esta coleção de vídeos se concentra nas estruturas, componentes, funções e requisitos do corpo humano. É complementada por vídeos de cientistas em ação que demonstram a aplicação desse conhecimento em instalações médicas e de pesquisa do mundo real.

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

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Meiosis II

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RNA Editing

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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

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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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