Name: cell cycle checkpoints and cyclin control
Uploaded: 2025-05-22T09:05:54.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Biology

BIO.6

BIO.6.A

The Cell Cycle Control System

يتميز نظام التحكم في دورة الخلية ببروتينات تنظيمية توقف دورة الخلية في G1 و G2 والمراحل الانقسامية.
إنها تساعد في منع بدء المرحلة التالية حتى تكتمل المراحل السابقة دون أي خطأ.
بالإضافة إلى ذلك ، تشكل هذه البروتينات المنظمة الرئيسية ، والتي تسمى كينازات البروتين المعتمدة على السيكلين أو Cdks ، مجمعات مع الأعاصير وتضمن تنسيق جميع المراحل وتوقيتها بشكل صحيح.
عند نقطة تفتيش G1 ، يتحقق البروتين التنظيمي مما إذا كانت الخلية قد وصلت إلى الحجم الحرج ، وأن الحمض النووي خال من الأخطاء ، وتوجد عناصر غذائية وعوامل نمو كافية للدخول في مرحلة S لتخليق الحمض النووي.
إذا لم تتلق الخلية الإشارة اللازمة ، فإنها تتحول إلى حالة الراحة أو مرحلة G0.
خلاف ذلك ، يتم تكرار الحمض النووي ، وتواجه الخلية نقطة تفتيش G2 ، حيث تتحقق البروتينات التنظيمية من وجود أخطاء في الحمض النووي قبل الدخول في الانقسام.
أثناء الانقسام ، بعد أن يتحقق البروتين التنظيمي من أن الكروموسومات متصلة بالمغزل ومحاذاة بدقة ، تشرع الخلية في الانقسام.
في أي مرحلة من دورة الخلية ، إذا اكتشف البروتين التنظيمي ضررا لا يمكن إصلاحه ، يحدث موت الخلايا.

نظام التحكم في دورة الخلية

<div style="direction:rtl">يوجّه نظام التحكم في دورة الخلية عملية انتقال الخلية من مرحلة إلى أخرى ويحفّز بدء الانقسام الميتوزي. يتضمن هذا النظام جزيئات تنظيمية داخل الخلية ومحفزات خارجية، حيث توفر هذه الجزيئات إشارات "التوقف" أو "التقدم"، وتعمل عند مراحل محددة من دورة الخلية تُعرف باسم نقاط الفحص، لضمان اكتمال كل عملية قبل انتقال الخلية إلى المرحلة التالية. السيكلينات والإنزيمات الكيناز المرتبطة بالسيكلين (CDKs) هما من بين أبرز المنظمين لدورة الخلية، حيث يؤديان دورًا رئيسيًا في مراحل G1 و G2 و M. تقوم المنظمات عند نقطة الفحص G1 بالتحقق من توفر الظروف المناسبة لتخليق الحمض النووي، مثل حجم الخلية وعوامل النمو. وإذا لم تستوفِ الخلية هذه المتطلبات، يتم منعها من الدخول في مرحلة S، مما يؤدي إما إلى توقفها عن الانقسام أو انتقالها إلى مرحلة G0 حتى تتحقق الشروط اللازمة. عند نقطة الفحص G2، يتم التحقق من أن الحمض النووي قد تم نسخه دون أخطاء أو أضرار. وإذا تم اكتشاف ضرر في الحمض النووي، تتدخل آليات الإصلاح قبل السماح للخلية بالانتقال إلى المرحلة التالية. أما عند نقطة الفحص M، فيتم التأكد من أن الكروموسومات الشقيقة قد اصطفت بشكل صحيح وارتبطت بـ الميكروتيبولات (الأنابيب الدقيقة) عند المستوى الاستوائي خلال الطور الاستوائي (ميتافاز). يضمن ذلك انتقال الخلية بأمان إلى مرحلة الأنافاز، مما يؤدي إلى انقسامها إلى خليتين ابنتين تحتويان على العدد الصحيح من الكروموسومات. إذا فشلت الخلية في أي من نقاط الفحص السابقة واستمرت في التقدم دون تصحيح الأخطاء، فقد تتراكم الطفرات والإصابات الجينية، مما قد يؤدي في النهاية إلى نمو غير مسيطر عليه أو تكوّن الأورام. هذا النص مقتبس م <a href="https://openstax.org/books/anatomy-and-physiology/pages/3-5-cell-growth-and-division">Openstax, Anatomy and Physiology 2e, Section 3.5: Section Title Cell Growth and Division</a></div>

يوجه تنظيم دورة الخلية كيفية انتقال الخلية من مرحلة إلى أخرى وتبدأ الانقسام. يشتمل نظام التحكم في دورة الخلية على ...

Education

JoVE Core

Anatomy and Physiology

التشريح وعلم وظائف الأعضاء

Unit 1

الوحدة الأولى

Essential Cellular Processes

العمليات الخلوية الأساسية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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 orderly.

The G1 checkpoint checks whether the cell is ready for DNA synthesis. It looks at conditions such as cell size and growth factors. If these needs are not met, the cell does not enter S phase. Instead, it may pause the cycle or move into G0 until the conditions improve.

The G2 checkpoint reviews the replicated DNA before the cell moves on. It checks for damage or copying errors. If problems are found, DNA repair mechanisms fix the damage before the cell continues.

The M phase checkpoint acts during metaphase. It checks that sister chromatids are correctly aligned and attached to microtubules at the equatorial plane. When this happens, the cell can move into anaphase and form two daughter cells with the same number of chromosomes.

If a cell passes through these checkpoints without correction, mutations can build up. Over time, this may lead to uncontrolled growth or tumor formation. For that reason, cell cycle checkpoints are important for keeping division accurate.

Cell Cycle Checkpoints and Cyclin Control

cell-cycle-checkpoints-and-cyclin-control

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 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...

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

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?

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overview of cell signaling

Cell Signaling Pathways and Responses

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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

Explore how cyclins, Cdks, and checkpoints regulate the cell cycle at G1, G2, and M phases to protect DNA and guide normal cell division.

Cell Cycle Checkpoints and Cyclin Control | 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.

What is the Cell Cycle?

The cell cycle refers to the sequence of events occurring throughout a typical cell&#8217;s life. In eukaryotic cells, the somatic cell cycle has two ...

Interphase

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the ...

Mitosis and Cytokinesis

In eukaryotes, the cell division cycle is divided into distinct, coordinated cellular processes that include cell growth, DNA replication/chromosome ...

Positive Regulator Molecules

To consistently produce healthy cells, the cell cycle&mdash;the process that generates daughter cells&mdash;must be precisely regulated.

Internal ...

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a ...

Cancer

Cancers arise due to mutations in genes involved in the regulation of cell division, which leads to unrestricted cell proliferation. Modern science and ...

Replication in Prokaryotes

Overview

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to ...

Replication in Eukaryotes

Overview

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high ...

Proofreading

Synthesis of new DNA molecules starts when DNA polymerase links nucleotides together in a sequence that is complementary to the template DNA strand. DNA ...

Mitogens and the Cell Cycle

Mitogens and their receptors play a crucial role in controlling the progression of the cell cycle. However, the loss of mitogenic control over cell ...

The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular ...

Explain the importance of the cell cycle to the growth of organisms, including an overview of the stages of the cell cycle and deoxyribonucleic acid (DNA) replication models.

Cellular Differentiation

How does a complex organism such as a human develop from a single cell? It all starts from a single fertilized egg which gives rise to a vast array of ...

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

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Cells Coordinate Growth and Proliferation

Cell size is a significant factor impacting cellular design, function, and fitness. There exists some internal coordination by which cells double their ...

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An Introduction to Molecular Developmental Biology

Molecular signals play a major role in the complex processes occurring during embryonic development. These signals regulate activities such as cell ...

An Introduction to Stem Cell Biology

Cells that can differentiate into a variety of cell types, known as stem cells, are at the center of one of the most exciting fields of science today. ...

iPS Cell Differentiation

The ability of induced pluripotent stem cells or iPSCs to differentiate into most body cell types has stimulated repair and regenerative medicine research ...

Embryonic Stem Cells

Embryonic stem (ES) cells were first discovered in mice in 1981 by Martin Evans. In 1998, James Thomson identified a method to isolate embryonic stem ...

Forced Transdifferentiation

Transdifferentiation, also known as lineage reprogramming, was first discovered by Selman and Kafatos in 1974 in silkmoths. They observed that the ...

Explain the process of cell specialization through cell differentiation, including the role of environmental factors.

BIO.6.B

Abnormal Proliferation

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Cancers Originate from Somatic Mutations in a Single Cell

Cancer arises from mutations in the critical genes that allow healthy cells to escape cell cycle regulation and acquire the ability to proliferate ...

Relate disruptions of the cell cycle to how they lead to the development of diseases such as cancer.

BIO.6.C

Science concepts--biological structures, functions, and processes. The student knows how an organism grows and the importance of cell differentiation. The student is expected to:

Cell Cycle Checkpoints and Cyclin Control

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