Cell Biology: Centrioles and Kinetochore Quiz
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Questions and Answers

During which phase of mitosis do chromosomes align at the metaphase plate?

  • Prometaphase
  • Telophase
  • Metaphase (correct)
  • Anaphase

    • What occurs during anaphase in mitosis?

  • Sister chromatids separate and move toward opposite poles (correct)
  • Daughter nuclei form at opposite ends
  • Spindle microtubules attach to kinetochores
  • Chromosomes replicate at the origin of replication

    • What is the primary form of cell division in prokaryotes?

  • Meiosis
  • Mitosis
  • Budding
  • Binary fission (correct)

    • What happens to the spindle microtubules during telophase?

    <p>They disassemble as daughter nuclei form</p> Signup and view all the answers

    What characteristic of the eukaryotic cell cycle control system allows it to halt until specific signals are received?

    <p>Presence of distinct checkpoints</p> Signup and view all the answers

    Which type of cells in the human body have the highest frequency of division?

    <p>Skin and intestinal epithelial cells</p> Signup and view all the answers

    What is a unique feature of prokaryotic DNA compared to eukaryotic DNA?

    <p>Circular genome called plasmid</p> Signup and view all the answers

    What initiates DNA replication in prokaryotic cells during binary fission?

    <p>Origin of replication</p> Signup and view all the answers

    What is the primary role of the mitotic spindle during mitosis?

    <p>To control chromosome movement</p> Signup and view all the answers

    Which of the following describes the function of the kinetochore?

    <p>It facilitates the movement of chromosomes along microtubules.</p> Signup and view all the answers

    What characterizes non-kinetochore microtubules during cell division?

    <p>They overlap and help elongate the cell.</p> Signup and view all the answers

    What occurs during metaphase regarding sister chromatids?

    <p>They are lined up at the metaphase plate.</p> Signup and view all the answers

    What happens to microtubules during the movement of chromosomes by the kinetochore?

    <p>They become shortened by depolymerization.</p> Signup and view all the answers

    Which component is crucial for the assembly of spindle microtubules?

    <p>Centrosome</p> Signup and view all the answers

    What does the term 'aster' refer to in mitosis?

    <p>A radial arrangement of microtubules</p> Signup and view all the answers

    What is the result of the spindle microtubules attaching to the kinetochores during prometaphase?

    <p>Chromosomes begin to be pulled apart.</p> Signup and view all the answers

    What is the main role of the mitotic spindle during mitosis?

    <p>It facilitates the separation of identical sister chromatids.</p> Signup and view all the answers

    What mechanism allows sister chromatids to move to opposite sides of the cell during anaphase?

    <p>Kinetochore movement along microtubules</p> Signup and view all the answers

    What occurs during telophase in a dividing cell?

    <p>The nuclear envelope reforms around daughter nuclei.</p> Signup and view all the answers

    In animal cells, how does cytokinesis primarily occur?

    <p>Via a cleavage furrow formed by a contractile ring.</p> Signup and view all the answers

    What distinguishes cytokinesis in plant cells from that in animal cells?

    <p>Plant cells form a cell plate, whereas animal cells form a cleavage furrow.</p> Signup and view all the answers

    What happens to the microtubules during the movement of sister chromatids in anaphase?

    <p>They shorten due to depolymerization.</p> Signup and view all the answers

    What is the primary function of the aster during mitosis?

    <p>To anchor the spindle microtubules.</p> Signup and view all the answers

    What triggers the completion of mitosis if the spindle fibers are not correctly attached?

    <p>The cell undergoes apoptosis.</p> Signup and view all the answers

    What happens if the kinetochore does not attach properly to spindle microtubules?

    <p>Anaphase is delayed due to a molecular signal.</p> Signup and view all the answers

    What is density-dependent inhibition?

    <p>A response in which crowded cells stop dividing.</p> Signup and view all the answers

    What does the G1 checkpoint primarily assess?

    <p>Cell size and nutrient availability.</p> Signup and view all the answers

    Which cells typically enter the G0 phase permanently?

    <p>Mature cardiac muscle cells and neurons.</p> Signup and view all the answers

    What is the primary role of the G2 checkpoint?

    <p>To check if DNA has been successfully replicated and is undamaged.</p> Signup and view all the answers

    The M checkpoint also referred to as the spindle checkpoint, ensures what?

    <p>Sister chromatids are correctly attached to spindle microtubules.</p> Signup and view all the answers

    What signal triggers a cell to enter the G1 phase from G0 phase?

    <p>An external growth factor.</p> Signup and view all the answers

    What is the fate of a cell that does not receive a go-ahead signal at the G1 checkpoint?

    <p>The cell will exit the cycle and enter G0 phase.</p> Signup and view all the answers

    What is required for the anaphase to proceed during cell division?

    <p>Kinetochore of sister chromatids must anchor to spindle fibers at opposite poles.</p> Signup and view all the answers

    How do cyclins and cyclin-dependent kinases (Cdk's) function in the cell cycle?

    <p>They promote cell cycle progression when bound together.</p> Signup and view all the answers

    What role do proto-oncogenes play in the cell cycle?

    <p>They code for proteins that promote positive regulation of the cell cycle.</p> Signup and view all the answers

    Which statement correctly describes tumor suppressor genes?

    <p>They code for negative regulator proteins.</p> Signup and view all the answers

    What is the primary function of cyclin-dependent kinases (Cdk's)?

    <p>To phosphorylate proteins necessary for cell cycle advancement.</p> Signup and view all the answers

    Which of the following phases is NOT part of interphase?

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

    What is one notable cause of cancer related to the cell cycle?

    <p>Dysregulation of genes affecting cell cycle control.</p> Signup and view all the answers

    Which protein is an example of a tumor suppressor gene product?

    <p>P53</p> Signup and view all the answers

    Study Notes

    Role of Centriole

    • Centrals facilitate the formation of the mitotic spindle, crucial for chromosome movement during mitosis.
    • The mitotic spindle, composed of microtubules, emerges from the centrosome, acting as the microtubule organizing center.
    • Asters, radial arrays of short microtubules, extend from each centrosome, resembling stars.
    • The spindle structure encompasses chromosomes, spindle microtubules, and asters, aiding in chromosome segregation.
    • Centroles at each end of the cell produce the spindle, which connects to chromosomes via kinetochores, not dragging chromosomes directly.

    The Kinetochore

    • The kinetochore is a protein complex associated with chromosome centromeres and serves as the attachment site for spindle microtubules.
    • Kinetochore movement facilitates chromosome segregation, operating along microtubules through depolymerization of tubulin.
    • During prometaphase, spindle microtubules attach to kinetochores, aligning chromosomes for movement.

    Metaphase

    • Chromosomes align at the metaphase plate, an imaginary line at the midpoint between spindle poles.
    • Sister chromatids are completely identical and are lined up for separation, with spindles attached from both sides.
    • This alignment is critical for the checkpoint ensuring proper separation; failure to do so halts mitosis.

    Anaphase

    • Sister chromatids separate and move toward opposite cell poles, facilitated by the kinetochore's movement along spindle microtubules.
    • Microtubules shorten through depolymerization, while non-kinetochore microtubules push against each other, assisting in cell elongation.

    Telophase

    • Daughter nuclei form at opposite ends of the cell, with a nuclear envelope reconstituting around the DNA.
    • Cytokinesis, the division of cytoplasm, often occurs simultaneously with telophase; in animal cells, it manifests as cleavage through a contractile ring of microfilaments.

    Binary Fission in Prokaryotes

    • Prokaryotes, like bacteria, undergo binary fission, a simpler division method wherein chromosomes replicate and the cell membrane pinches inward.
    • Bacterial colonies appear as genetically identical clones on agar plates.

    Cell Cycle Control System

    • The eukaryotic cell cycle is governed by a molecular control system, regulating division frequency based on cell type, with skin and intestinal cells dividing rapidly.
    • Checkpoints act like a clock, ensuring conditions are right for cell cycle progression.

    G1, G2, and M Checkpoints

    • G1 Checkpoint: Determines if a cell proceeds to the S phase; failure leads to entry into the non-dividing G0 phase.
    • G2 Checkpoint: Assesses cell size and DNA integrity before mitotic phase entry, halting the cycle for DNA repair if needed.
    • M Checkpoint (Spindle Checkpoint): Ensures kinetochores are correctly attached to spindle microtubules before anaphase begins.

    Cyclins and Cyclin-Dependent Kinases (Cdk's)

    • Cyclins and Cdk's are key regulators of the cell cycle, activating progression through various checkpoints when bound together.
    • Cdk enzymes phosphorylate target proteins, altering their shape for activation, facilitating the transition to the next cell cycle phase.

    Cancer Cell Dynamics

    • Proto-oncogenes promote normal cell cycle progression, but mutations can convert them to oncogenes, causing cancerous growth.
    • Tumor suppressor genes, like P53, code for proteins that inhibit uncontrolled cell division, playing a protective role against cancer development.

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    Description

    Test your knowledge on the critical roles of centrioles and kinetochores in cell division. This quiz covers mitotic spindles, chromosome movement, and the function of microtubules. Perfect for students studying cell biology and mitosis.

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