Cell Cycle and Interphase: Regulation and Checkpoints
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Questions and Answers

During which phase of mitosis does the nuclear envelope break down, allowing microtubules to contact kinetochores?

  • Metaphase
  • Prophase
  • Prometaphase (correct)
  • Telophase

What is the primary function of the Anaphase Promoting Complex (APC) during anaphase?

  • Condensing chromosomes in preparation for cell division
  • Inactivating mitotic cyclin-dependent kinase (M-Cdk) (correct)
  • Synthesizing new nuclear envelopes around daughter chromosomes
  • Facilitating chromosome replication

At which stage of mitosis are sister chromatids split into two identical sets of chromosomes?

  • Anaphase (correct)
  • Telophase
  • Metaphase
  • Prophase

Which cellular component is responsible for physically separating the daughter chromosomes during anaphase?

<p>The mitotic spindle (A)</p> Signup and view all the answers

What event directly follows telophase in the cell cycle?

<p>Cytokinesis (B)</p> Signup and view all the answers

If a cell has 20 picograms of DNA in G1 phase, how many picograms of DNA will it have after S phase, assuming complete replication?

<p>40 (B)</p> Signup and view all the answers

Which of the following events occurs during telophase?

<p>The nuclear envelope reforms (B)</p> Signup and view all the answers

What is the immediate consequence of cohesion destruction during mitosis?

<p>Sister chromatid separation (B)</p> Signup and view all the answers

Which event is LEAST likely to occur during prophase?

<p>Nuclear envelope breakdown. (C)</p> Signup and view all the answers

What is the primary role of cohesin during prophase?

<p>To prevent damage to chromatids. (D)</p> Signup and view all the answers

What is the IMMEDIATE result of the abrupt increase in M-Cdk activity during prophase?

<p>Initiation of mitotic events. (A)</p> Signup and view all the answers

How would the absence of M-Cdk affect prometaphase?

<p>The nuclear envelope would not break down. (C)</p> Signup and view all the answers

What event characterizes the transition from prometaphase to metaphase?

<p>Alignment of chromosomes at the metaphase plate. (B)</p> Signup and view all the answers

During metaphase, what force ensures sister chromatids align at the metaphase plate?

<p>Motor proteins pulling chromosomes in opposite directions. (B)</p> Signup and view all the answers

If motor proteins on kinetochore microtubules malfunctioned during metaphase, what would be the MOST likely outcome?

<p>Failure of chromosome alignment at the metaphase plate. (D)</p> Signup and view all the answers

Which statement accurately describes the relative duration of the phases?

<p>Metaphase lasts about half the duration of mitosis. (B)</p> Signup and view all the answers

Which of the following accurately describes the role of microtubules in cell division?

<p>Microtubules ensure proper chromosome alignment and segregation during spindle formation. (B)</p> Signup and view all the answers

How does cytokinesis differ between plant and animal/fungi cells?

<p>Plant cells form a cell plate via vesicle fusion, while animal/fungi cells use actin-myosin contraction to form a cleavage furrow. (D)</p> Signup and view all the answers

What is the primary function of the actin-myosin contractile ring during cell division?

<p>To cause the plasma membrane to pinch inward, dividing the cytoplasm. (B)</p> Signup and view all the answers

If a cell is treated with an antimitotic agent during metaphase, what would be the most likely outcome?

<p>The cell would be unable to properly align chromosomes and segregate them into daughter cells. (D)</p> Signup and view all the answers

Taxol is an antimitotic drug that affects microtubule function. What is the most likely reason it is used in cancer treatment?

<p>It disrupts microtubule function, inhibiting the cell cycle of rapidly dividing cells like cancer cells. (C)</p> Signup and view all the answers

Which of the following represents the correct sequence of events during cell division?

<p>Anaphase, Telophase, Cytokinesis (A)</p> Signup and view all the answers

How does the genetic material in the two daughter cells compare after cytokinesis, assuming normal cell division?

<p>Each daughter cell has identical genetic material to each other and to the parent cell. (A)</p> Signup and view all the answers

What would be the immediate consequence if the Golgi apparatus were non-functional during cytokinesis in a plant cell?

<p>The cell plate would not form properly, preventing cell division. (C)</p> Signup and view all the answers

Taxanes exert their anti-cancer effect by which of the following mechanisms?

<p>Stabilizing microtubules, preventing their breakdown and disrupting cell division. (A)</p> Signup and view all the answers

Vinca alkaloids, such as vincristine and vinblastine, disrupt cell division by:

<p>Binding to tubulin subunits and preventing their polymerization. (C)</p> Signup and view all the answers

Which of the following accurately describes the role of M-Cdk in the cell cycle?

<p>It controls the early part of the M-phase and is later inactivated by APC. (B)</p> Signup and view all the answers

How do antimitotic agents selectively target cancer cells compared to normal cells?

<p>They preferentially disrupt the cell cycle in rapidly dividing cells, like cancer cells. (D)</p> Signup and view all the answers

During which phase of the cell cycle do taxanes primarily exert their effect?

<p>Metaphase (D)</p> Signup and view all the answers

If a researcher wants to study the effects of a drug that prevents chromosomal segregation, which phase of the cell cycle should they focus on?

<p>M phase (D)</p> Signup and view all the answers

A scientist observes that cells treated with a certain drug are unable to form the mitotic spindle. Which of the following drugs is most likely responsible for this effect?

<p>A drug that stabilizes microtubules excessively (D)</p> Signup and view all the answers

Which of the following cellular processes is directly inhibited by both Vinca alkaloids and Colchicine?

<p>Microtubule polymerization (C)</p> Signup and view all the answers

Which of the following outcomes is LEAST directly ensured by the cell cycle checkpoints?

<p>The absence of any mutations in daughter cells. (B)</p> Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

<p>S phase (D)</p> Signup and view all the answers

A researcher observes a cell population with an increased rate of aneuploidy. Which cell cycle checkpoint is most likely malfunctioning in these cells?

<p>Metaphase checkpoint, ensuring proper chromosome alignment. (A)</p> Signup and view all the answers

What is the primary function of mitosis (M phase) in somatic cells?

<p>Distributing chromosomes to daughter cells (D)</p> Signup and view all the answers

In multicellular organisms, the purpose of cell division does NOT include:

<p>sexual reproduction. (A)</p> Signup and view all the answers

If a toxin inhibits cytokinesis, but not mitosis, what outcome would you expect to observe in treated cells?

<p>Cells with multiple nuclei. (B)</p> Signup and view all the answers

Which of the following describes the state of a cell in the G0 phase?

<p>In a resting or quiescent state, outside the active cell cycle (A)</p> Signup and view all the answers

A mutation causes a cell to bypass the G1 checkpoint. What is the most likely consequence of this mutation?

<p>The cell will divide uncontrollably, even with DNA damage. (D)</p> Signup and view all the answers

What cellular process primarily occurs during the G1 phase of the cell cycle?

<p>Growth and metabolism (A)</p> Signup and view all the answers

Consider a drug that interferes with the function of the mitotic spindle. At which specific phase of the cell cycle would this drug most likely arrest cells?

<p>Metaphase. (A)</p> Signup and view all the answers

If a mammalian cell spends approximately 10-12 hours in S phase, what percentage of the total cell cycle does this represent?

<p>50% (D)</p> Signup and view all the answers

Sister chromatids are joined together at what specialized region of the chromosome?

<p>Centromere (A)</p> Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

<p>S phase (B)</p> Signup and view all the answers

What is primarily monitored during the gap phases (G1 and G2) of interphase?

<p>Intracellular and extracellular environment and signals (A)</p> Signup and view all the answers

Which of the following best describes the primary function of the G2 checkpoint?

<p>Verifying that DNA replication is complete and accurate before mitosis. (A)</p> Signup and view all the answers

What is the significance of the checkpoint in the G1 phase?

<p>It determines if the environment is favorable for cell division. (C)</p> Signup and view all the answers

If a cell with damaged DNA proceeds through the G1 checkpoint, which of the following outcomes is most likely?

<p>The cell may attempt DNA replication with errors, potentially leading to mutations. (B)</p> Signup and view all the answers

How does the duration of the M phase compare to the other phases of the cell cycle in mammalian cells?

<p>M phase is relatively short compared to interphase. (D)</p> Signup and view all the answers

Flashcards

Interphase

A nondividing phase of the cell cycle including G1, S, and G2 phases.

G1 phase

The first gap phase where the cell grows and synthesizes proteins and organelles.

S phase

The synthesis phase where DNA replication occurs and chromosomes are duplicated.

G2 phase

The second gap phase where the cell prepares for mitosis, including the growth of structural elements.

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G0 phase

A resting phase where mature cells (like muscle cells and neurons) exit the active cell cycle.

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Sister chromatids

Identical copies of a chromosome joined together at the centromere following DNA replication.

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Centromere

The specialized region of a chromosome where sister chromatids are joined together.

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Mitosis (M) phase

The phase of the cell cycle where the nucleus divides to distribute chromosomes to daughter cells.

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Cytokinesis

The process occurring after mitosis, where the cytoplasm divides to form two daughter cells.

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Chromosome distribution

The process of evenly distributing replicated chromosomes to daughter cells during mitosis.

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Cell Cycle

A sequence of events leading to two identical daughter cells.

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G1 Checkpoint

A checkpoint before entering the S phase of the cell cycle.

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G2 Checkpoint

A checkpoint before entering the M phase of the cell cycle.

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Mitosis

The division of the nucleus during the M phase.

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Checkpoints

Regulatory points that ensure proper cell cycle progression.

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Aneuploidy

A condition with an abnormal number of chromosomes in a cell.

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Subphases of M phase

M phase consists of Prophase, Prometaphase, Metaphase, Anaphase, and Telophase.

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Prophase

The first subphase where chromosomes become visible as sister chromatids.

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Prometaphase

The phase where the nuclear envelope breaks down and microtubules attach to chromatids.

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Metaphase

The phase where chromosomes align at the spindle equator.

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M-Cdk

Mitotic cyclin dependent kinase crucial for mitosis regulation.

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Anaphase

The phase where sister chromatids separate and move toward opposite poles.

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Telophase

The final stage of mitosis where new nuclear envelopes form around each set of chromosomes.

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Anaphase Promoting Complex (APC)

A regulatory complex that triggers the transition from metaphase to anaphase.

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Mitotic Arrest

A halt in the cell cycle during mitosis, preventing cell division.

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Paclitaxel

An antimitotic drug used in cancer chemotherapy, stabilizing microtubules.

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Vinca alkaloids

A class of chemotherapy drugs that prevent tubulin polymerization, halting cell division.

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Colchicine

An antimitotic agent that disrupts microtubule formation by binding tubulin.

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Cell Cycle Phases

Divided into G1, S, G2 (interphase) and M - essential for cell division.

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Antimitotic Agents

Drugs that affect microtubule dynamics, often used in cancer treatment.

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Actin-myosin ring

Structure that causes the plasma membrane to pinch in during cytokinesis in animal cells.

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Cytokinesis in plants

Plants form a cell plate from vesicles during cytokinesis.

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Cytokinesis in animals

Animals use a cleavage furrow formed by actin-myosin contraction for cell division.

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Microtubules

Hollow structures made of tubulin dimers that facilitate intracellular transport and chromosome movement.

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Study Notes

Cell Cycle Overview

  • The cell cycle is a series of intracellular events leading to the production of two identical daughter cells
  • The genetic code is passed along
  • All living organisms are products of repeated cell division rounds
  • Unicellular organisms reproduce through binary fission
  • Multicellular organisms divide for growth, repair, and replacement

Cell Cycle Checkpoints

  • The cell cycle is regulated by checkpoints
  • G1 checkpoint: before entering S phase
  • G2 checkpoint: before entering M phase
  • Metaphase checkpoint: during cell division
  • Checkpoints control orderly progression, high-fidelity DNA replication, DNA damage repair, and correct chromosome segregation
  • Problems like aneuploidy (extra or missing chromosomes) and mutations can disrupt the cell cycle

Interphase: G Phases

  • Interphase includes G1, S, and G2 phases
  • G1 phase: initial growth and metabolic phase
  • S phase: DNA replication
  • G2 phase: growth and synthesis of structural elements
  • G0 is a resting phase where some cells (e.g., mature muscle cells, neurons) remain outside the active cell cycle

Interphase: G Phases - Detailed

  • G phases are important for organelle replication and cytoplasmic expansion in preparation for division.
  • During these phases, cells also monitor internal and environmental conditions
  • Cells that don't proceed through the checkpoints can either delay or arrest their cycle by entering the G0 phase.
  • Unfavorable environments can also initiate cell cycle arrest

Interphase: S Phase

  • S phase is the cell synthesis phase where DNA replication takes place.
  • DNA copies are called sister chromatids and are joined together in a specialized region named the centromere.
  • Packaging proteins are also replicated during this stage

Mitosis (M) Phase

  • Mitosis is a stage of nucleus division, often accompanied by cytokinesis (cytoplasm division).
  • Aims to distribute chromosomes to daughter cells.
  • Replicated chromosomes are equally divided.
  • Two daughter nuclei with identical chromosomes and genes are formed

Mitosis (M) Phase - Subphases

  • Mitosis is a continuous process with five subphases (PPMAT)
  • Prophase: Chromosomes condense, centrosomes move to opposite poles
  • Prometaphase: Nuclear envelope breaks down, microtubules attach to chromosomes
  • Metaphase: Chromosomes align at the metaphase plate in the center of the cell.
  • Anaphase: Sister chromatids separate and move to opposite poles
  • Telophase: Chromosomes decondense, nuclear envelopes re-form

Mitosis (M) phase - Cytokinesis

  • Cytoplasm division completes cell division
  • Each daughter cell receives a complete set of organelles and genetic material.
  • In animal cells, a contractile ring of actin-myosin filaments pinches the cell membrane inward (cleavage furrow) to create two separate cells
  • In plants, vesicles from the Golgi apparatus fuse to form a cell plate creating a new cell wall.

Antimitotic Agents

  • Drugs that interfere with mitosis
  • Affect microtubule assembly and disassembly.
  • Examples: Taxols (e.g., Paclitaxel, Docetaxel), Vinca alkaloids (e.g., Vincristine, Vinblastine), Colchicine, and Nocodazole.
  • Used for cancer treatment targeting rapidly dividing cells
  • MOA involves disrupting microtubule function and arresting cells in metaphase

Summary of Cell Cycle & Mitosis

  • Cell cycle consists of interphase (G1, S, G2) and the mitotic (M) phase.
  • The M-phase involves replicated chromosome segregation, and formation of two daughter nuclei
  • Prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis are the phases of M-phase
  • Anti-mitotic agents target microtubules to inhibit cell division for cancer treatment

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Cell Cycle PDF

Description

Explore the cell cycle, a series of events producing identical daughter cells. Learn about checkpoints (G1, G2, metaphase) that regulate DNA replication, repair, and chromosome segregation. Understand interphase, including G1 (growth), S (DNA replication), and G2 (synthesis) phases.

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