Name: cell cycle checkpoints and regulation
Uploaded: 2023-04-30T18:28:50.000Z
Duration: 2 min 11 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Life Science

Inheritance and Variation of Traits

3.1.9-12.D

The Cell Cycle Control System

The cell cycle involves the duplication of the intracellular content, followed by the division into two daughter cells.
Replication of cellular content, especially the DNA, is highly critical, and any mistake during the process can lead to conditions such as cancer.&#160;
So how do cells prevent any errors during division?
The cell cycle control system features regulator proteins that halt the cycle at various checkpoints.
At every checkpoint, the regulator proteins prevent the initiation of each step until the earlier stages are completed and any errors have been corrected.
Generally, the control system has three crucial checkpoints found in the G1, G2, and M phases.
At the G1 checkpoint, the regulator protein checks if the cell has reached the critical size and the DNA is free from errors. It also checks whether enough nutrients and growth factors are present to begin DNA synthesis.
At this point, if the cell does not receive the necessary signal, it switches to a resting state called the G0 phase until all the conditions are met.
The cells that pass the G1 checkpoint transit through the synthesis, or S-phase, when the DNA gets replicated.
After this, the cell encounters a second checkpoint at the G2 phase, where the regulator proteins check any errors in the DNA and whether the cell has an appropriate size to enter Mitosis or M-phase.
During Mitosis, the control system verifies if the chromosomes are attached to the spindle and are accurately aligned so that the cycle proceeds for cell division. If at any point the regulator protein detects irreparable damage, cell death occurs. One type of critical regulator proteins are the cyclin-dependent protein kinases, or CDK. CDKs form complexes with cyclins, and their activity affects proteins directly involved in cell growth and DNA synthesis.

the cell cycle control system

The cell cycle is an organized set of events that leads the cell to divide into two daughter cells, each containing chromosomes identical to the parent cell. It is the cell cycle that leads to the formation of an entire organism from a single-cell zygote. Besides, cell division also functions in the renewal or repair of tissues in adult multicellular eukaryotes. For example, in the bone marrow, the stem cells divide to form new blood cells. Although essential for several functions, cell division in the absence of a control mechanism leads to cancer and many genetic diseases.
To ensure DNA replication occurs correctly and each daughter cell inherits the right number of chromosomes, the cell has surveillance mechanisms that make up the cell cycle control system. There are at least two known cell cycle control methods. One of these processes includes a cascade of protein phosphorylations that transitions a cell from one phase to the next. Also, there is a series of checkpoints that monitor the completion of essential events and, if necessary, delay progression to the next phase. At every checkpoint, the regulator proteins prevent the cell initiation from entering the next phase until the previous phase&#39;s errors are rectified.
The first form of regulation includes a highly regulated family of kinases. Kinase activation requires interaction with a second subunit expressed at fixed points of the cell cycle. This secondary component is termed as- a phase-specific &#34;cyclin&#34;&#160; that combines with its partner &#34;cyclin-dependent kinase&#34; (CDK), forming an active complex, each of which exhibits distinct substrate specificity. Regulatory phosphorylation and dephosphorylation fine-tune the function of cyclin-CDK complexes, ensuring a well-defined progression.
The second form of cell cycle regulation - checkpoint control, is more of a surveillance mechanism. Cell cycle checkpoints identify defects in crucial events such as DNA replication and chromosome segregation. For instance, DNA damage triggers a signaling cascade that activates several cell cycle inhibitors. These inhibitors bind critical cell cycle proteins to arrest the cycle until the risk of mutation has been eliminated.

The cell cycle is an organized set of events that leads the cell to divide into two daughter cells, each containing chromosomes identical to the parent ...

Education

JoVE Core

Cell Biology

Unit 1

Cell Proliferation

KEY TERMS AND CONCEPTS

cell cycle checkpoints and regulation

The cell cycle is controlled by checkpoints and regulator proteins that help cells divide in an orderly way. These controls monitor whether a cell is ready to move from one stage to the next. They help prevent division from continuing when conditions are not right.

The control system depends on proteins that can either encourage or block progress through the cycle. Some of these regulators act as signals that push the cell forward. Others act as brakes that slow the cycle when problems are detected.

Checkpoints are important because they let the cell pause and respond before division continues. This control is part of how cells keep the cycle coordinated. It also helps maintain normal cell growth and division.

Cell Cycle Checkpoints and Regulation

what is the cell cycle?

Cell Cycle Stages and Checkpoints

The cell cycle is the set of events that a typical eukaryotic cell goes through during its life. In somatic cells, it has two main stages: interphase and the mitotic phase. Interphase is the time when the cell grows, carries out basic metabolic functions, copies its DNA, and gets ready to divide. The mitotic phase comes next. During mitosis, the nucleus divides, and during cytokinesis, the cytoplasm divides. These steps produce two daughter cells that are identical to the original parent cell.

interphase

Cell Growth Phases Before Mitosis

Interphase is the part of the cell cycle when a eukaryotic cell grows and gets ready for mitosis. In a typical human cell, the full cell cycle lasts about 24 hours. Interphase makes up about 95 percent of that time and includes three stages: G1, S, and G2. After mitosis and cytokinesis, cells enter G1, or gap 1. During this stage, cells grow continuously and prepare for DNA replication. They are metabolically active and copy important organelles and biochemical molecules, including proteins. <br...

The cell cycle is controlled by checkpoints and regulator proteins that help cells divide in an orderly way. These controls monitor whether a cell is ready to move from one stage to the next. They help prevent division from continuing when conditions are not right. The control system depends on proteins that can either encourage or block progress through the cycle. Some of these regulators act as signals that push the cell forward. Others act as brakes that slow the cycle when problems are...

positive regulator molecules

Positive Regulators in Cell Growth

Positive regulator molecules help cells move through the cell cycle. The cell cycle is the series of steps a cell uses to grow and divide. These molecules act as signals that support progress through each stage. Two important examples are cyclins and cyclin-dependent kinases, or CDKs. Cyclins are proteins that rise and fall during the cell cycle. CDKs are enzymes that work with cyclins to help control cell-cycle events. Together, these positive regulators help the cell advance when conditions...

inhibition of cdk activity

How CDK Inhibitors Slow Cell Division

Cyclin-dependent kinase (CDK) inhibitors slow cell division by blocking CDK activity. CDKs are enzymes that help control the cell cycle, which is the series of steps a cell follows to grow and divide. When CDKs are inhibited, the cycle can pause instead of moving forward. The video focuses on this control point in cell growth. CDK inhibition is important because it helps regulate when cells enter the next stage of the cycle. By stopping CDK activity, cells do not continue dividing at the wrong...

s-cdk initiates dna replication

S-Cdk Starts the DNA Copying Process

S-Cdk starts the DNA copying process by triggering DNA replication. S-Cdk is a cyclin-dependent kinase that helps move the cell into S phase, the part of the cell cycle when DNA is copied. This step matters because the cell must begin replication at the right time. S-Cdk adds phosphate groups to target proteins, which changes their activity and helps turn on the machinery needed for DNA synthesis. The result is that replication can begin in a controlled way. This process is an important part...

m-cdk drives transition into mitosis

M-Cdk Triggers the Start of Mitosis

M-Cdk triggers the start of mitosis by helping a cell move from interphase into division. It is a key cell-cycle regulator that turns on the mitotic program at the right time. The M-Cdk complex includes a cyclin and a cyclin-dependent kinase. When this complex becomes active, it sends signals that push the cell into mitosis. This step helps control when chromosomes begin to condense and the nuclear changes of division can begin. Understanding M-Cdk is important because it links cell-cycle...

mitogens and the cell cycle

Mitogen Signals in Cell Division

Mitogens are signals that help cells move through the cell cycle. The cell cycle is the set of stages a cell follows to grow and divide. In many cells, mitogens are needed before the cell can enter division. These signals work through pathways inside the cell. One important route is the MAP kinase signaling pathway, which helps pass the mitogen message from the cell surface to the cell’s interior. This signaling helps the cell respond and continue through the cycle. Mitogens are closely tied...

replicative cell senescence

Telomere Shortening and Cell Aging

Replicative cell senescence is a form of cell aging linked to repeated cell division. As cells divide, their telomeres shorten. Telomeres are protective DNA caps at the ends of chromosomes. When telomeres become too short, cells can no longer keep dividing in the same way. The cell enters senescence, a state in which it stays alive but stops dividing. This process helps explain how division limits can affect cell growth over time.

abnormal proliferation

Unchecked Cell Growth Patterns

Abnormal proliferation is a pattern of cell growth that does not follow normal control. In healthy tissue, cells divide only when they are needed. When that control is lost, cells can keep multiplying in an unusual way. This kind of cell growth can be seen in different settings. It may involve cells that divide too fast, too often, or when they should stop. The result is tissue that grows in a way that no longer matches the body’s normal balance. Understanding abnormal proliferation helps...

cells coordinate growth and proliferation

cells-coordinate-growth-and-proliferation

Cell Size Homeostasis and Checkpoints

Cells coordinate growth and proliferation to keep cell size under control. Growth increases cell mass, while proliferation creates new cells. Together, these processes help cells maintain size homeostasis, which means keeping a stable size over time. The cell cycle includes a checkpoint called the size checkpoint. At this point, the cell checks whether it has grown enough before it divides. This control helps connect growth with cell division, so cells do not become too small or too large. <br...

key terms and concepts

Learn how checkpoints and regulator proteins control the cell cycle, helping cells divide in order and pause when conditions are not right.

Cell Cycle Checkpoints and Regulation | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Louisiana Student Standards for Science

High School

Life Sciences

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

From Molecules To Organisms: Structures And Processes

HS-LS1-4

Tennessee Academic Standards

Biology

From Molecules to Organisms: Structures and Processes

BIO1.LS1.6

Minnesota Academic Standards in Science

2.2.1 9L.2.2.1.2

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Arizona Science Standards

HS.L1

HS.L1U1.22

Alabama Course of Study Science

9-12.B.1.3

Florida Department of Education

SC.912.L.16

SC.912.L.16.8

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 ...

Positive Regulator Molecules

Inhibition of CDK Activity

Mitosis and Cytokinesis

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

Chromosome Duplication

Cohesins

Condensins

The Mitotic Spindle

Centrosome Duplication

Spindle Assembly

Attachment of Sister Chromatids

Forces Acting on Chromosomes

Separation of Sister Chromatids

The Spindle Assembly Checkpoint

Anaphase A and B

Anaphase Promoting Complex

The Contractile Ring

Determining the Plane of Cell Division

The Phragmoplast

Distribution of Cytoplasmic Content

An Introduction to Cell Division

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell ...

Cell Cycle Analysis

Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the ...

Live Cell Imaging of Mitosis

Mitosis is a form of cell division in which a cell&#8217;s genetic material is divided equally between two daughter cells. Mitosis can be broken down into ...

Fertilization

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Cleavage and Blastulation

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Gastrulation

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Neurulation

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Cell Migration

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an-introduction-to-developmental-genetics

An Introduction to Developmental Genetics

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Fate Mapping

Fate mapping is a technique used to understand how embryonic cells divide, differentiate, and migrate during development. In classic fate mapping ...

Students who demonstrate understanding can use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.  Assessment Boundary: Assessment does not include specific gene control mechanisms or rote memorization of the steps of mitosis.

DNA Packaging

DNA as a Genetic Template

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Organization of Genes

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

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The centromere is a DNA ...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

The Nucleosome

DNA in a human cell is almost 2m long and it is packed inside a tiny nucleus that is only a few microns in diameter. The level of compaction of DNA inside ...

The Nucleosome Core Particle

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Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA ...

Chromatin Packaging

Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 ...

Karyotyping

Proteins: From Genes to Degradation

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

The Central Dogma

The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
RNA is the Missing Link Between ...

Mutations

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Genome Size and the Evolution of New Genes

Gene Families

Students who demonstrate understanding can ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.

3.1.9-12.P

Genomic DNA in Prokaryotes

The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the ...

Binary Fission

Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the ...

Genomic DNA in Eukaryotes

Eukaryotes have large genomes compared to prokaryotes. To fit their genomes into a cell, eukaryotic DNA is packaged extraordinarily tightly inside the ...

What is Meiosis?

Meiosis is the process by which diploid cells divide to produce haploid daughter cells. In humans, each diploid cell contains 46 chromosomes, half from ...

Meiosis I

Meiosis is a carefully orchestrated set of cell divisions, the goal of which&#x2014;in humans&#x2014;is to produce haploid sperm or eggs, each containing ...

Meiosis II

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 ...

Crossing Over

Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where ...

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed ...

Base-pairing and DNA Repair

The DNA Replication Fork

Lagging Strand Synthesis

The Replisome

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template ...

Replication in Prokaryotes

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Replication in Eukaryotes

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Telomeres and Telomerase

background-and-environment-affect-phenotype

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

Gene Evolution - Fast or Slow?

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Types of Genetic Transfer Between Organisms

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

Students who demonstrate understanding can make and defend a claim based on evidence that inheritable genetic variations may result from (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.

3.1.9-12.Q

What is Population Genetics?

A population is composed of members of the same species that simultaneously live and interact in the same area. When individuals in a population breed, ...

Students who demonstrate understanding can apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population. Assessment Boundary: Assessment does not include Hardy-Weinberg calculations.

3.1.9-12.R

Cell Cycle Checkpoints and Regulation

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