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

מערכת בקרת מחזור התא כוללת חלבונים רגולטוריים שעוצרים את מחזור התא בשלבים G1, G2 ומיטוטיים.
הם עוזרים למנוע את התחלת השלב הבא עד להשלמת השלבים המוקדמים יותר ללא כל שגיאה.
בנוסף, חלבונים מווסתי מפתח אלה, הנקראים קינאזות חלבון תלויות ציקלין או Cdks, יוצרים קומפלקסים עם ציקלינים ומוודאים שכל השלבים מתואמים ומתוזמנים כראוי.
במחסום G1, החלבון המווסת בודק אם התא הגיע לגודל הקריטי, הדנ"א נקי משגיאות, וקיימים מספיק חומרים מזינים וגורמי גדילה כדי להיכנס לשלב S לסינתזה של DNA.
אם התא אינו מקבל את האות הדרוש, הוא עובר למצב מנוחה או לשלב G0.
אחרת, הדנ"א משוכפל, והתא נתקל במחסום G2, שבו חלבוני הבקרה בודקים שגיאות בדנ"א לפני הכניסה למיטוזה.
במהלך מיטוזה, לאחר שהחלבון המווסת מוודא שהכרומוזומים מחוברים לציר ומיושרים במדויק, התא ממשיך לחלוקה.
בכל נקודה במחזור התא, אם החלבון המווסת מזהה נזק בלתי הפיך, מתרחש מוות תאי.

מערכת בקרת מחזור התא

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וויסות מחזור התא מכוון כיצד תא מתקדם משלב אחד לאחר ומתחיל במיטוזה. מערכת בקרת מחזור התא כוללת מולקולות ויסות תוך תאיות וטריגרים חיצוניים. הם מספקים אותות עצירה או קדמה ופועלים בשלבי מחזור תא ספציפיים המכונים נקודות ביקורת כדי להבטיח שתהליך מסוים יושלם לפני שהתא מתקדם לשלב הבא.

ציקלינים וקינאזות תלויות ציקלין (Cdks) הם מווסתי מחזור התא העיקריים ומתפקדים בשלבי מחזור התא G1, G2 ו-M. הרגולטורים במחסום G1 מוודאים שתנאים מתאימים זמינים לסינתזת DNA, כגון גודל תא וגורמי גדילה. אם תא אינו עומד בדרישות אלה, נמנע ממנו להיכנס לשלב S. התא או עוצר את מחזור התא או עובר לשלב G0 עד לסיפוק צרכיו. הרגולטורים במחסום G2 מוודאים שה-DNA המשוכפל נקי מכל נזק או שגיאה; אחרת, מנגנון תיקון ה-DNA מתקן את הנזק ולאחר מכן מאפשר לתא להתקדם לשלב הבא. הרגולטורים של מחסום הפאזה M מבטיחים שהכרומטידות האחיות מיושרות ומחוברות בצורה נכונה למיקרוטובוליות במישור המשווני של המטאפאזה. זה מאפשר לתא להתקדם לשלב האנפאזה של חלוקת התא ולייצר שני תאי בת עם מספר שווה של כרומוזומים.

אם תא נכשל באחת מנקודות הבידוק לעיל וממשיך להתקדם דרך מיטוזה, הוא צובר מוטציות שעלולות להוביל בסופו של דבר לצמיחה בלתי מבוקרת או להיווצרות גידול.

הטקסט הזה מותאם מ <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>
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ויסות מחזור התא מכוון כיצד התא מתקדם משלב אחד למשנהו ומתחיל מיטוזה. מערכת בקרת מחזור התא כוללת ...

Education

JoVE Core

Anatomy and Physiology

אנטומיה ופיזיולוגיה

Unit 1

יחידה 1

Essential Cellular Processes

תהליכים תאיים חיוניים

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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

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translation

Translation: mRNA to Protein

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How Cells Control Gene Expression

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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

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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?

Meiosis and the Formation of Gametes

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overview of cell signaling

Cell Signaling Pathways and Responses

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cellular differentiation

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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

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Proofreading

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Mitogens and the Cell Cycle

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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

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Cell Diversity

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

BIO.6.B

Abnormal Proliferation

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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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