Name: cell cycle checkpoints and cancer
Uploaded: 2025-08-06T09:37:54.000Z
Duration: 1 min 4 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.2.1

What is the Cell Cycle?

מחזור התא מתייחס לרצף של אירועים לאורך כל דרך החיים של צמיחת התא, שכפול דנ"א, לפעמים יותר צמיחה וחלוקה. לשחזור מיני אורגניזמים, החיים מתחילים כזיגוטה, ביצה מופרית. במשך הזמן, התא המקורי והבודד גדל ומתחלק באחוזה מבוקרת בכדי לייצר תאים רבים, נדרש אדם מורכב.תאים ממשיכים את התהליך הזה, במיוחד כדי לתחזק ולתקן רקמות במהלך תהליך ההזדקנות. לעומת זאת, תא בודד אורגניזמים כמו חיידקים, מסתמך על חלוקת התא פשוט להשתכפל באמצעות ביקוע בינארי. למרבה הצער כאשר התא חלוקה נותרה ללא בדיקה, חוזרות תוצאות סרטן עם אובדן שליטה על רצפים גנומיים כדי לווסת את התהליך הרגיל.

שר, צ'ארלס ג'יי וג'ירי ברטק. "מחזור התא – טיפולים ממוקדים בסרטן". סקירה שנתית של ביולוגיה של סרטן 1, מס '1 (2017): 41–57. [<a href="https://doi.org/10.1146/annurev-cancerbio-040716-075628" target="__blank">מקור</a>]

מהו מחזור התא?

<div style="direction:rtl">מחזור התא מתייחס לרצף האירועים המתרחשים במהלך חייו של תא טיפוסי. בתאים איקריוטים, למחזור התא הסומטי יש שני שלבים: אינטרפאזה ושלב המיטוזה. במהלך האינטרפאזה, התא גדל, מבצע את הפונקציות המטבוליות הבסיסיות שלו, מעתיק את ה-DNA שלו ומתכונן לחלוקת תאים מיטוטי. לאחר מכן, במהלך מיטוזה וציטוקינזה, התא מחלק את החומרים הגרעיניים והציטופלסמיים שלו, בהתאמה. חלוקה זאת יוצרת שני תאי בת זהים לתא האב המקורי. מחזור התא חיוני לצמיחת האורגניזם, החלפת תאים פגומים והתחדשות של תאים מיושנים. סרטן הוא תוצאה של חלוקת תאים בלתי מבוקרת שנוצרת על ידי מוטציה גנטית. <h4>נקודות בקרה במחזור התא</h4> ישנן שלוש נקודות בקרה עיקריות במחזור התא האוקריוטי. בכל אחת מהן ניתן לעצור את ההתקדמות לשלב הבא במחזור התא עד לתנאים נוחים יותר. שלב G1 הוא הראשון שבהם, שבו מוערכים גודל התא, האנרגיה, החומרים המזינים, איכות ה-DNA וגורמים חיצוניים אחרים. אם התא נחשב כלא מתאים, הוא אינו ממשיך לשלב S של אינטרפאזה. שלב G2 הוא הנקודה השנייה. כאן, התא מבטיח שכל ה-DNA שוכפל ולא ניזוק לפני הכניסה למיטוזה. אם מתגלה נזק ל-DNA שאינו ניתן לתיקון, התא עלול לעבור אפופטוזיס, או מוות תאי מתוכנן. נקודת ה-M או הציר מבטיח שכל הכרומטידות האחיות מחוברות בצורה נכונה למיקרוטובוליות של הציר בלוח המטאפאזה לפני שהתא נכנס לאנפאזה. <h4>סרטן: כאשר מחזור התא משתבש</h4> נקודות הבקרה למחזור התא מבטיחות שתאים בריאים עוברים דרך מחזור התא בצורה מווסתת. עם זאת, תאי סרטן עוקפים לעתים קרובות את המחסומים הללו. כל סבב עוקב של חלוקת תאים לא מבוקרת מייצר יותר תאי בת פגומים. בנוסף, תאים סרטניים בגוף האדם יכולים להתחלק הרבה יותר פעמים מאשר תאים רגילים, שיכולים לעבור רק כ-40-60 סבבי חלוקה. תאים סרטניים מבטאים טלומראז, אנזים המתקן את הבלאי בקצוות הכרומוזומים, הנגרם בדרך כלל מחלוקת תאים.</div>

מחזור התא מתייחס לרצף האירועים המתרחשים לאורך חייו של תא טיפוסי. בתאים אאוקריוטים, מחזור התא הסומטי יש שני ...

Education

JoVE Core

ביולוגיה

Cellular Processes

תהליכים תאיים

Cell Cycle and Division

מחזור התא והחלוקה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

cell cycle checkpoints and cancer

The cell cycle is the set of steps a eukaryotic cell follows as it grows and divides. In somatic cells, it has two main stages: interphase and the mitotic phase. During interphase, the cell grows, carries out its basic metabolic functions, copies its DNA, and gets ready for mitotic cell division.

After interphase, the cell enters mitosis and cytokinesis. Mitosis divides the nuclear material, and cytokinesis divides the cytoplasm. These steps produce two daughter cells that are identical to the original parent cell.

The cell cycle is important for many body processes. It supports growth, replaces damaged cells, and helps regenerate older cells. When the cycle is disrupted by a gene mutation, uncontrolled cell division can lead to cancer.

Eukaryotic cells also use checkpoints to control cell cycle progress. The G1 checkpoint checks cell size, energy, nutrients, DNA quality, and other external factors before the cell enters S phase. The G2 checkpoint confirms that DNA has been fully copied and is not damaged before mitosis begins. If damage cannot be repaired, the cell may undergo apoptosis, or programmed cell death.

The M checkpoint, also called the spindle checkpoint, acts during mitosis. It makes sure the sister chromatids are properly attached to spindle microtubules at the metaphase plate before anaphase starts. These checkpoints help healthy cells divide in a regulated way, but cancer cells often bypass them. As a result, each round of unchecked division can create more damaged daughter cells, and cancer cells may divide far more times than normal cells, which usually complete about 40 to 60 divisions. Cancer cells also express telomerase, an enzyme that helps repair chromosome ends worn down by repeated cell division.

Cell Cycle Checkpoints and Cancer

what is the cell cycle?

The cell cycle is the set of steps a eukaryotic cell follows as it grows and divides. In somatic cells, it has two main stages: interphase and the mitotic phase. During interphase, the cell grows, carries out its basic metabolic functions, copies its DNA, and gets ready for mitotic cell division. After interphase, the cell enters mitosis and cytokinesis. Mitosis divides the nuclear material, and cytokinesis divides the cytoplasm. These steps produce two daughter cells that are identical to the...

genomic dna in prokaryotes

Prokaryote Chromosomes and Plasmids

Most prokaryotes store their DNA in one circular chromosome inside the nucleoid, a region of cytoplasm. This chromosome is double-stranded and tightly wound, or supercoiled, so it fits efficiently inside the cell. Prokaryotes also carry smaller circular DNA pieces called plasmids. Plasmids often carry genes that give bacteria helpful traits. One important example is antibiotic resistance. Bacteria can gain these plasmids and the traits they carry, which can help them adapt to changing...

binary fission

How Cells Split by Binary Fission

Binary fission is a common way that bacteria and archaea reproduce. In this process, one parent cell divides into two parts. Each new cell can then grow to the size of the original parent cell. This is an asexual form of reproduction, so the cells produced are genetically identical. Binary fission can happen very fast. In the time it takes one bacterial cell to divide, the number of cells in the culture doubles. That time is called the doubling time. Escherichia coli cells often divide every...

genomic dna in eukaryotes

How Eukaryotic DNA Fits Inside the Nucleus

Eukaryotic DNA fits inside the nucleus by packing into a highly compact form. Eukaryotes have large genomes compared with prokaryotes, so their DNA must be tightly organized to fit inside one cell. The process starts when DNA wraps around proteins called histones. These DNA-histone units form nucleosomes, which are connected by linker DNA. The nucleosomes then coil into chromatin fibers, and additional fibrous proteins compact the chromatin even more. This packed material is called chromatin,...

interphase

Interphase in the Cell Growth Cycle

Interphase is the stage of the cell cycle when a eukaryotic cell grows and copies its DNA before mitosis. In a typical human cell, the full cell cycle takes about 24 hours, and interphase makes up about 95 percent of that time. It is followed by mitosis, also called M, when the cell divides. After mitosis and cytokinesis, cells enter the G1 phase, or gap 1. During G1, cells grow continuously and prepare for DNA replication. They are metabolically active and copy essential organelles and...

mitosis and cytokinesis

Cell Cycle Stages in Mitosis

Cell cycle stages in mitosis show how a eukaryotic cell copies its DNA and then divides into two daughter cells. The cycle is controlled by regulatory systems and by outside signals that affect cell growth and division. In typical human cells, the full cycle takes about 24 hours and includes two major phases. The first is DNA replication during the S phase of interphase. The second is the mitotic, or M, phase, which includes mitosis and cytokinesis. G1 and G2 are the gap stages between these...

positive regulator molecules

Cyclins and CDKs in the Cell Cycle

Cyclins and CDKs help control the cell cycle, the process that produces daughter cells. Cells use internal checkpoints to make sure their size, energy reserves, and DNA are ready before they move forward. At these checkpoints, positive regulators help the cell continue, while negative regulators slow or stop it. The main positive regulators are cyclins and cyclin-dependent kinases, or CDKs. These proteins are found in eukaryotes, from yeast to humans. Cyclins are grouped by the stage they help...

negative regulator molecules

Cell Cycle Stop Signals: p53, p21, and Rb

Cell cycle stop signals help control when a cell can move forward through division. Negative regulators pause or end the cell cycle until the cell meets the right conditions. Three well-studied negative regulators are p53, p21, and retinoblastoma protein, or Rb. Their roles became clear after faulty versions were found in cancer cells that kept replicating uncontrollably. These proteins act mostly at the G1 checkpoint, which comes early in the cell cycle. P53 has a strong effect on whether a...

cancer

Cancer Treatment, Personalization, and Cell Growth

Cancer develops when mutations affect genes that control cell division. Those changes can remove the normal brakes on growth and lead to uncontrolled cell proliferation. Modern science and medicine have improved how cancer is understood and treated, and some patients can now be cured. There is still no single cure for cancer because cancer is not one disease. It is a large group of many diseases. Even when two people have the same mutation in an oncogene or a tumor suppressor gene, their...

key terms and concepts

Learn how the cell cycle is controlled by G1, G2, and M checkpoints, and how checkpoint failure and telomerase activity can contribute to cancer.

Cell Cycle Checkpoints and Cancer | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

Pennsylvania State Academic Standards

Life Science

Inheritance and Variation of Traits

3.1.9-12.Q

Virginia  Standards of Learning

HIgh School

BIO.3

BIO.3.c

LS.2

LS.2.d

Next Generation Science Standards

High School

From Molecules to Organisms: Structures and Processes

HS-LS1-4

Texas Essential Knowledge and Skills

BIO.6

BIO.6.A

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS1-4.

myJoVE Corporation

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Prokaryotic Cells

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Cytoplasm

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The Nucleus

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Endoplasmic Reticulum

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Ribosomes

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Golgi Apparatus

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Lysosomes

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Peroxisomes

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overview-of-myosin-structure-and-function

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LS.Bio.1.3

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the-tree-of-life-bacteria-archaea-and-eukaryotes

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LS.Bio.1.5

Analyze how the relationship between structure and function supports life processes within organisms.

Cell Cycle Checkpoints and Cancer

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