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Questions and Answers
What is the primary purpose of the cell cycle?
What is the primary purpose of the cell cycle?
Which phase of the cell cycle is characterized by DNA replication?
Which phase of the cell cycle is characterized by DNA replication?
What occurs during the G1 phase of interphase?
What occurs during the G1 phase of interphase?
What is the final checkpoint in interphase?
What is the final checkpoint in interphase?
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Which stage of mitosis involves the lining up of chromosomes along the metaphase plate?
Which stage of mitosis involves the lining up of chromosomes along the metaphase plate?
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During which phase do chromatin condense into visible chromosomes?
During which phase do chromatin condense into visible chromosomes?
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What is the result of mitosis?
What is the result of mitosis?
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What happens to the nuclear envelope during prophase?
What happens to the nuclear envelope during prophase?
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What ensures each daughter cell receives one copy of each chromosome during metaphase?
What ensures each daughter cell receives one copy of each chromosome during metaphase?
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What occurs at the end of telophase?
What occurs at the end of telophase?
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What occurs during the S phase of interphase?
What occurs during the S phase of interphase?
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Which event is characteristic of prophase in the cell cycle?
Which event is characteristic of prophase in the cell cycle?
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What happens to sister chromatids during anaphase?
What happens to sister chromatids during anaphase?
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What is the function of the cleavage furrow in telophase?
What is the function of the cleavage furrow in telophase?
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How do telomeres affect cell division as we age?
How do telomeres affect cell division as we age?
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What role do ATM genes play in the cell cycle?
What role do ATM genes play in the cell cycle?
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What is the primary function of cyclin-dependent kinases (CDKs) during the cell cycle?
What is the primary function of cyclin-dependent kinases (CDKs) during the cell cycle?
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What is the purpose of the G2/M checkpoint in the cell cycle?
What is the purpose of the G2/M checkpoint in the cell cycle?
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What are motor proteins responsible for during anaphase?
What are motor proteins responsible for during anaphase?
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What happens to chromatin during telophase?
What happens to chromatin during telophase?
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What is the main activity taking place during the S phase of interphase?
What is the main activity taking place during the S phase of interphase?
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What structural change occurs to chromatin during prophase?
What structural change occurs to chromatin during prophase?
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Which phase immediately follows metaphase in mitosis?
Which phase immediately follows metaphase in mitosis?
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What is the role of microtubules during metaphase?
What is the role of microtubules during metaphase?
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What occurs during cytokinesis?
What occurs during cytokinesis?
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What happens to the cell during the G2 phase of interphase?
What happens to the cell during the G2 phase of interphase?
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Which of the following best describes telophase?
Which of the following best describes telophase?
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During which stage of mitosis do microtubules attach to the kinetochores?
During which stage of mitosis do microtubules attach to the kinetochores?
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What is the significance of the centromere during mitosis?
What is the significance of the centromere during mitosis?
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What occurs during the G1 phase of interphase?
What occurs during the G1 phase of interphase?
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What are sister chromatids?
What are sister chromatids?
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Which of the following best describes a microtubule organizing center (MTOC)?
Which of the following best describes a microtubule organizing center (MTOC)?
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What is the primary function of the cleavage furrow?
What is the primary function of the cleavage furrow?
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Which type of cells typically do not divide after they are formed?
Which type of cells typically do not divide after they are formed?
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What happens to telomeres with each DNA replication?
What happens to telomeres with each DNA replication?
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Which checkpoint ensures that conditions are favorable for DNA replication?
Which checkpoint ensures that conditions are favorable for DNA replication?
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What is cell senescence?
What is cell senescence?
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What role do APC proteins play in the cell cycle?
What role do APC proteins play in the cell cycle?
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Which cells are classified as proliferative cells?
Which cells are classified as proliferative cells?
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What is the G2/M checkpoint's primary function?
What is the G2/M checkpoint's primary function?
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What is primarily produced during the G1 phase of interphase?
What is primarily produced during the G1 phase of interphase?
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What significant process occurs during the S phase?
What significant process occurs during the S phase?
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Which type of cells can re-enter the cell cycle if stimulated?
Which type of cells can re-enter the cell cycle if stimulated?
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Which phase of mitosis is characterized by chromatin condensing into visible chromosomes?
Which phase of mitosis is characterized by chromatin condensing into visible chromosomes?
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What ensures that the cell has adequate resources to proceed to the S phase?
What ensures that the cell has adequate resources to proceed to the S phase?
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Which stages significantly involve the mitotic spindle?
Which stages significantly involve the mitotic spindle?
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What occurs during cytokinesis?
What occurs during cytokinesis?
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Which cells are classified as permanent cells?
Which cells are classified as permanent cells?
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Which cellular function primarily occurs during the G2 phase?
Which cellular function primarily occurs during the G2 phase?
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What is the role of proto-oncogenes in the cell cycle?
What is the role of proto-oncogenes in the cell cycle?
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What is the main event that occurs during anaphase?
What is the main event that occurs during anaphase?
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Which structure forms during prophase and is essential for chromosome movement?
Which structure forms during prophase and is essential for chromosome movement?
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What is formed during telophase that signifies the end of mitosis?
What is formed during telophase that signifies the end of mitosis?
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Which proteins assist in moving chromosomes along microtubules during mitosis?
Which proteins assist in moving chromosomes along microtubules during mitosis?
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During which phase is the cytoplasm divided to create two separate daughter cells?
During which phase is the cytoplasm divided to create two separate daughter cells?
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What happens to the chromosomes during telophase?
What happens to the chromosomes during telophase?
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What is the primary function of the kinetochore?
What is the primary function of the kinetochore?
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Which phase of the cell cycle is directly preceding anaphase?
Which phase of the cell cycle is directly preceding anaphase?
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Which of the following best describes the roles of actin and myosin during cytokinesis?
Which of the following best describes the roles of actin and myosin during cytokinesis?
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What can trigger cells in G0 phase to re-enter the cell cycle?
What can trigger cells in G0 phase to re-enter the cell cycle?
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Study Notes
The Cell Cycle
- The cell cycle is the process by which a cell replicates itself, creating two identical daughter cells.
- It's essential for growth, development, and repair.
- The cell cycle is split into two main phases: interphase and mitosis.
Interphase
- Interphase is the period of growth and preparation for mitosis.
- It's further divided into three subphases: G1 phase, S phase, and G2 phase.
G1 Phase (Gap 1)
- The cell increases in size and synthesizes new organelles.
- It also produces proteins and enzymes needed for DNA replication.
- Cells spend most of their time in G1 phase.
S Phase (Synthesis)
- DNA replication occurs in the S phase.
- This is when DNA is duplicated, creating two identical sets of chromosomes.
- Errors in DNA replication are checked and corrected.
- The S phase typically lasts about 6 hours.
G2 Phase (Gap 2)
- The cell prepares for mitosis by continuing to synthesize proteins and enzymes.
- The cell grows further, ensuring there is enough cytoplasm for division.
- It's a final checkpoint to ensure DNA replication was successful and the cell is ready to divide.
Mitosis
- Mitosis is the division of the nucleus, which results in two daughter nuclei with the same number of chromosomes as the parent cell.
- It's divided into four stages: prophase, metaphase, anaphase, and telophase.
- Cytokinesis, the division of the cytoplasm, occurs at the end of telophase.
Prophase
- Chromatin condenses, becoming visible as chromosomes.
- Each chromosome consists of two identical sister chromatids held together by a centromere.
- The nuclear envelope breaks down and the mitotic spindle, made of microtubules, starts to form.
Metaphase
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The mitotic spindle fibers attach to the centromeres of the chromosomes.
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Chromosomes line up along the center of the cell called the metaphase plate.
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This ensures that each daughter cell receives one copy of each chromosome.
Cell Cycle Phases
-
Interphase
- Chromatin is loose within the nucleus
- DNA replication occurs during the S phase
- Results in 4n DNA content at the end
-
Prophase
- Chromatin condenses
- Nuclear envelope breaks down
- Microtubule organizing centers (MTOC) appear, containing centrioles
-
Metaphase
- MTOC migrate to opposite poles of the cell
- Microtubules attach to chromosomes at the kinetochore
- Chromosomes align along the metaphase plate
-
Anaphase
- Sister chromatids separate and move to opposite poles of the cell
- Microtubules shorten
- Cohesin proteins are cleaved to separate chromatids
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Telophase
- Nuclear envelope reforms
- Chromatin decondenses
- Cleavage furrow forms as the cell begins to divide
- Cytokinesis results in two daughter cells with equal cytoplasm and organelles
Chromosome Structure
- Chromosome is made up of chromatin (DNA and histone proteins)
- Sister chromatids are two identical copies of a chromosome
- Centromere is the region that joins sister chromatids, determining the number of chromosomes
- Telomeres are the ends of chromosomes
Cell Cycle Regulation
-
G0 Phase
- Cells enter a quiescent state and remain dormant
- May reenter the cell cycle if stimulated
- Stable cells often reside in this phase
Important Proteins
- Cyclin-dependent kinases (CDKs) phosphorylate proteins involved in nuclear envelope breakdown and chromatin condensation
- Motor proteins (Dynein and Kinesin) move chromatids towards the poles of the cell during anaphase
- Actin and Myosin proteins form the contractile ring for cytokinesis
Cell Cycle
- Some cells lose the ability to proliferate once they've reached maturity, for example neurons, skeletal muscle cells, and cardiac muscle cells.
- Telomeres located at the ends of chromosomes shorten with each DNA replication.
- As we age, the shortening of telomeres can lead to a state called cell senescence where cells are permanently out of the cell cycle.
- The G2 phase of the cell cycle takes approximately 2 hours.
- The G2/M checkpoint ensures that DNA replication has been completed without errors.
- ATM genes play a critical role in the G2/M checkpoint by producing proteins that monitor DNA integrity.
- The M checkpoint, located during metaphase, checks for proper alignment of chromosomes at the metaphase plate.
- The correct alignment of chromosomes guarantees that sister chromatids separate accurately during anaphase.
- APC proteins and Securin are involved in the M checkpoint, regulating the progression of the cell cycle.
The Cell Cycle
- The process of cell replication, essential for organismal growth, development, and repair.
- Divided into two main phases: interphase (preparation) and mitosis (division).
Interphase
- A period of cell growth and preparation for division.
- Further subdivided into three phases: G1 phase, S phase, and G2 phase.
G1 Phase (Gap 1)
- Characterized by cell growth and synthesis of new organelles.
- Essential proteins and enzymes for DNA replication are produced.
- Cells primarily spend time in this phase.
S Phase (Synthesis)
- DNA replication occurs, resulting in two identical sets of chromosomes.
- Errors in DNA replication are monitored and corrected.
- Typically lasts approximately 6 hours.
G2 Phase (Gap 2)
- The cell prepares for mitosis, continuing protein synthesis and enzyme production.
- The cell expands further, ensuring sufficient cytoplasm for division.
- A final checkpoint ensuring accurate DNA replication and readiness for cell division.
Mitosis
- Nuclear division resulting in two identical daughter nuclei, each with the same chromosome number as the parent cell.
- Divided into four distinct stages: prophase, metaphase, anaphase, and telophase.
- Cytokinesis, the cytoplasm division, occurs at the end of telophase.
Prophase
- Chromatin condenses, becoming visible as chromosomes.
- Each chromosome comprises two identical sister chromatids joined at the centromere.
- The nuclear envelope breaks down, and the mitotic spindle, composed of microtubules, starts to form.
Metaphase
- Mitotic spindle fibers attach to chromosome centromeres.
- Chromosomes align along the cell's center, known as the metaphase plate, ensuring each daughter cell receives a complete set of chromosomes.
Anaphase
- Sister chromatids separate and move towards opposite poles of the cell.
- Microtubules shorten, pulling chromatids apart.
- Cohesin proteins that held chromatids together are cleaved.
Telophase
- The nuclear envelope reforms around the separated chromosomes.
- Chromatins decondense, becoming less tightly packed.
- A cleavage furrow forms, initiating cell division.
- Cytokinesis results in two daughter cells, each with equal cytoplasm and organelles.
Cell Cycle Phases
-
Interphase
- Chromatin is loosely dispersed in the nucleus.
- DNA replication takes place during the S phase.
- Results in a 4n DNA content at the end.
-
Prophase
- Chromatin condenses into visible chromosomes.
- The nuclear envelope breaks down.
- Microtubule organizing centers (MTOC) appear, containing centrioles.
-
Metaphase
- MTOC migrate to opposite poles of the cell.
- Microtubules attach to chromosomes at the kinetochore.
- Chromosomes align along the metaphase plate.
-
Anaphase
- Sister chromatids separate and move to opposite poles of the cell.
- Microtubules shorten, pulling chromatids apart.
- Cohesin proteins are cleaved to separate chromatids.
-
Telophase
- Nuclear envelope reforms around the separated chromosomes.
- Chromatins decondense.
- Cleavage furrow forms as the cell begins to divide.
- Cytokinesis results in two daughter cells with equal cytoplasm and organelles.
Chromosome Structure
- Chromosomes are composed of chromatin, a complex of DNA and histone proteins.
- Sister chromatids are two identical copies of a chromosome.
- Centromere is the region that joins sister chromatids, influencing the chromosome count.
- Telomeres are protective structures found at the ends of chromosomes.
Cell Cycle Regulation
-
G0 Phase
- Cells enter a quiescent state and remain dormant.
- May re-enter the cell cycle when stimulated.
- Stable cells often reside in this phase.
Important Proteins
- Cyclin-dependent kinases (CDKs) phosphorylate proteins crucial for events like nuclear envelope breakdown and chromatin condensation.
- Motor proteins (Dynein and Kinesin) facilitate the movement of chromatids towards the cell poles during anaphase.
- Actin and Myosin proteins form the contractile ring responsible for cytokinesis.
Cell Cycle Continued
- Some cells lose the ability to proliferate after reaching maturity, for example, neurons, skeletal, and cardiac muscle cells.
- Telomeres located at chromosome ends shorten with each DNA replication.
- As we age, telomere shortening may lead to "cell senescence," a state where cells are permanently out of the cell cycle.
- The G2 phase of the cell cycle typically lasts around 2 hours.
- The G2/M checkpoint ensures the completion of DNA replication without errors.
- ATM genes play a vital role in the G2/M checkpoint by producing proteins that monitor DNA integrity.
- The M checkpoint, occurring during metaphase, verifies proper chromosome alignment at the metaphase plate.
- Accurate chromosome alignment ensures that sister chromatids segregate correctly during anaphase.
- APC proteins and Securin contribute to the M checkpoint, regulating cell cycle progression.
The Cell Cycle
- The cell cycle is the process cells use to replicate and grow.
- It is divided into two main phases: interphase and mitosis.
Interphase
- Interphase is further divided into three phases: G1, S, and G2.
- G1 phase:
- The first phase of interphase.
- The cell increases the number of organelles and synthesizes proteins and enzymes needed for DNA replication.
- Repairs thymine dimers in DNA.
- Cells spend a significant amount of time in this phase.
- S phase:
- Stands for "synthesis."
- DNA replication occurs within a replication bubble.
- DNA polymerase accurately replicates DNA.
- Typically lasts for 6 hours.
- G2 phase:
- Cell growth phase.
- Increases the cytoplasm to prepare for cell division.
- Cells need to be large enough to divide evenly.
Mitosis
- Mitosis divides a cell into two identical daughter cells.
- The four phases of mitosis are prophase, metaphase, anaphase, and telophase.
- Cytokinesis occurs at the end of telophase.
Prophase
- Chromatin condenses into chromosomes.
- Chromatin is made up of DNA and histone proteins.
- Condensation is crucial for proper separation of chromosomes during later stages.
Cell Cycle Phases
- Interphase: Chromatin is loose, DNA replicates, cell prepares for division.
- Prophase: Chromatin condenses into chromosomes, nuclear envelope breaks down, microtubule organizing center forms.
- Metaphase: Chromosomes align on the metaphase plate, microtubule organizing centers move to opposite poles of the cell, microtubules (polar microtubules) attach to kinetochores on chromosomes.
- Anaphase: Sister chromatids separate (cohesin protein is split), microtubules pull chromatids to opposite poles.
- Telophase: Nuclear envelope reforms, chromosomes decondense, cleavage furrow forms.
- Cytokinesis: Cleavage furrow completes, cytoplasm divides, two daughter cells are formed.
Important Terms
- Chromatin: DNA and histone proteins in the nucleus.
- Chromosome: Condensed chromatin during mitosis.
- Centromere: Point of attachment for microtubule fibers.
- Kinetochore: Proteins that connect microtubules to chromosomes.
- Sister chromatids: Replicated copies of a chromosome joined at the centromere.
- Microtubule organizing center (MTOC): Contains centrioles and serves as a source for microtubule growth.
- Cleavage furrow: Indentation of the cell membrane that divides the cytoplasm.
- Cytokinesis: Division of the cytoplasm.
Cell Cycle Variations
- G0 phase: Cells are in a non-dividing state but can be re-stimulated to enter the cell cycle.
- Proliferative cells: Cells that regularly divide and enter the cell cycle.
- Stable cells: Cells that typically don't divide but can be re-stimulated to enter the cell cycle.
- Permanent cells: Cells that don't divide after they are formed (e.g., neurons).
Cell Cycle Details
- Neurons, skeletal muscle, and cardiac muscle do not proliferate once fully developed.
- Telomeres are protective ends of chromosomes.
- Telomeres shorten with each DNA replication.
- Cell senescence is an irreversible state where cells exit the cell cycle and can no longer proliferate, often due to shortened telomeres.
- The G2/M checkpoint ensures that DNA replication has been completed without errors.
- ATM genes produce proteins that detect and repair DNA damage during the G2/M checkpoint.
- The M checkpoint (spindle checkpoint) ensures that chromosomes are properly aligned at the metaphase plate before entering anaphase.
- APC proteins help regulate the M checkpoint, ensuring proper separation of chromosomes.
- The G1/S checkpoint ensures that conditions are favorable for DNA replication.
The Cell Cycle
- The cell cycle is a series of stages a cell goes through to replicate itself, creating two identical daughter cells.
- It's essential for both growth and controlling cell proliferation.
- The cycle is divided into two major phases: interphase and mitosis.
Interphase
- Interphase is further divided into three phases: G1, S, and G2.
- G1 Phase (Gap 1): The cell grows, produces organelles, synthesizes proteins and enzymes, and repairs DNA damage. Most cells spend the majority of their time in this phase.
- S Phase (Synthesis): The cell replicates its DNA, ensuring each daughter cell gets a complete set of chromosomes. This phase typically takes about six hours.
- G2 Phase (Gap 2): The cell continues to grow, producing necessary proteins to support cell division.
Types of Cells and their Relationship to the Cell Cycle
- Labile Cells: Continuously replicate throughout their lifespan (examples: skin cells, cells in the GI tract, urinary tract, and hematopoietic stem cells).
- Stable Cells: Don't divide frequently, but can re-enter the cycle if stimulated (examples: liver cells, kidney tubules, and lung cells).
- Permanent Cells: Don't divide after reaching maturity (examples: neurons, skeletal and cardiac muscle cells).
G1/S Checkpoint
- Ensures the cell has enough resources, proper DNA structure, and the right conditions to proceed to DNA replication (S phase).
- Regulated by tumor suppressor genes and proto-oncogenes.
Mitosis (M Phase)
- Prophase: Chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and the mitotic spindle forms at the poles of the cell.
- Metaphase: Chromosomes align at the center of the cell, forming the metaphase plate, with spindle fibres attached to centromeres.
- Anaphase: Sister chromatids separate and move to opposite poles, ensuring each daughter cell receives an identical set of chromosomes.
- Telophase: The nuclear envelope reforms, chromosomes decondense, and cytokinesis begins, dividing the cytoplasm.
- Cytokinesis: The cytoplasm divides, completing the creation of two separate daughter cells.
Cell Cycle Phases
- The cell cycle is a continuous process of growth and division.
- The cell cycle stages are interphase, prophase, metaphase, anaphase, and telophase.
- Chromatin is loosely packed DNA with associated proteins.
- Chromosomes are condensed chromatin made of two sister chromatids.
- The centromere is the central point of a chromosome where the sister chromatids connect.
- Sister chromatids are two identical copies of a chromosome formed during DNA replication.
- Telomeres are the ends of chromosomes.
- The nuclear envelope is a membrane that encloses the nucleus.
- Microtubule organization centers (MTOCs) are structures that organize microtubules, which are composed of tubulin protein.
- Centrosomes are structures within MTOCs that organize microtubules.
- Spindle fibers are made of microtubules and are involved in chromosome movement during mitosis.
- Kinetochores are protein structures on the centromere where spindle fibers attach.
- Motor proteins, such as dynein and kinesin, help move chromosomes along microtubules.
- Cleavage furrow is a constriction formed in the cell membrane during cytokinesis, the division of the cytoplasm.
- Actin and myosin, contractile proteins, help create the cleavage furrow.
Key Facts about Interphase
- Chromatin is loosely packed.
- DNA replication occurs in the S phase.
- The cell grows and produces organelles in G1 and G2.
Key Facts about Prophase
- Chromatin condenses into chromosomes.
- The nuclear envelope dissolves.
- The mitotic spindle apparatus, made of microtubules, begins to form.
- The centrosomes, with centrioles, separate and move to opposite poles of the cell.
Key Facts about Metaphase
- Chromosomes are aligned at the metaphase plate, the center of the cell.
- Spindle fibers attach to the kinetochore, a protein complex on the centromere of each chromosome.
Key Facts about Anaphase
- Sister chromatids separate and are pulled to opposite poles of the cell by shortening spindle fibers.
- Motor proteins help move chromosomes along microtubules.
Key Facts about Telophase
- Chromosomes reach the poles of the cell and start decondensed, forming a new nuclear envelope around them.
- The cytoplasm divides, forming two daughter cells.
- The cleavage furrow, made of actin and myosin, pinches in the cell membrane, separating the cytoplasm of the daughter cells.
Cell Cycle Checkpoints
- Post-mitotic cells are cells unable to proliferate any longer (examples: neurons, skeletal muscle cells, and cardiac muscle cells).
- Telomeres, ends of chromosomes, shorten with each DNA replication, which can cause cells to enter cell senescence (a state where they stop actively dividing).
- The G2 phase of the cell cycle takes approximately two hours.
- There are three major checkpoints in the cell cycle: G1/S checkpoint, G2/M checkpoint, and M checkpoint.
- The G2/M checkpoint ensures there are no errors in DNA replication from the prior S phase. ATM genes play a role in this checkpoint.
- The M checkpoint occurs at metaphase, ensuring proper alignment of chromosomes at the metaphase plate before proceeding to anaphase.
- This checkpoint is regulated by proteins like APC and Securin.
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Description
Explore the fundamental stages of the cell cycle, including interphase and mitosis. Understand the critical phases such as G1, S, and G2, along with their roles in cell replication and preparation. This quiz is essential for students studying biology and cellular processes.
