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Questions and Answers

What is the role of the kinase Wee1?

  • it phosphorylates Cdc26
  • it phosphorylates M-Cdk to inactivate it (correct)
  • it dephosporylates M-Cdk to activate it
  • it ubiquitinates p53 it phosphorylates cyclins
  • The anaphase-promoting complex (APC) triggers the onset of anaphase by:

  • cleaving spindle microtubules.
  • phosphorylating the motor proteins that pull the spindle poles apart.
  • triggering the destruction of Cohesins that hold the sister chromatids together. (correct)
  • triggering the destruction of the condensins that hold the duplicated chromosomes in a condensed state. All of the above
  • The activation of M-Cdk begins abruptly, mainly because:

  • M-cyclin is bound to M-Cdk and the complex dephosphorylated by Cdc25 (correct)
  • M cyclin decreases abruptly
  • M cyclin gene transcription is rapidly activated
  • M-Cdk gene transcription is rapidly increased All of the above
  • What process is necessary in llate G1 phase to transition to S phase?

    <p>extracellular signals (mitogens) are activated</p> Signup and view all the answers

    Place the cell cycle in the correct order.

    <p>G1-S-G2-M</p> Signup and view all the answers

    What would be the consequence of a Wee1 gene mutation that prevents the protein from being translated?

    <p>it would keep the M-cyclin/M-Cdk complex active</p> Signup and view all the answers

    Which cell cycle phase is the shortest?

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

    Meiosis I has which feature?

    <p>All of the above</p> Signup and view all the answers

    The nuclear envelope breaks down at the start of prometaphase because:

    <p>Lamins are phosphorylated, which leads to filament dissociation.</p> Signup and view all the answers

    Which event triggers a pause in G1 phase?

    <p>the presence of DNA damage</p> Signup and view all the answers

    Study Notes

    Cell Cycle Regulation

    • Wee1 kinase inhibits M-Cdk activation, ensuring that mitosis is delayed until the DNA is fully replicated and checked for errors.

    Anaphase Onset

    • The anaphase-promoting complex (APC) triggers the onset of anaphase by ubiquitinating and degrading securin, which releases separase to cleave cohesion, allowing sister chromatids to separate.

    M-Cdk Activation

    • M-Cdk activation begins abruptly because Wee1 kinase, which inhibits M-Cdk, is inactivated, and Cdc25, which activates M-Cdk, is activated.

    G1 Phase Transition

    • The transition from G1 to S phase requires the activation of S-Cdk, which phosphorylates and inhibits Rb, allowing E2F to activate transcription of genes necessary for DNA replication.

    Cell Cycle Order

    • The correct order of the cell cycle is: G1 → S → G2 → M.

    Wee1 Gene Mutation

    • A Wee1 gene mutation that prevents the protein from being translated would lead to uncontrolled M-Cdk activation, causing premature entry into mitosis, which can result in chromosomal instability and cancer.

    Cell Cycle Phases

    • The shortest phase of the cell cycle is mitosis (M phase).

    Meiosis I Feature

    • Meiosis I is characterized by the reductional division, where the number of chromosomes is halved.

    Nuclear Envelope Breakdown

    • The nuclear envelope breaks down at the start of prometaphase because of phosphorylation of lamin by M-Cdk, allowing chromatin to condense and interact with the mitotic spindle.

    G1 Phase Pause

    • A pause in G1 phase can be triggered by the presence of DNA damage or other cellular stresses, which activate the p53 tumor suppressor protein to induce cell cycle arrest.

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    Description

    This quiz covers the regulation of the cell cycle, including the role of Wee1 kinase, M-Cdk activation, and the anaphase-promoting complex (APC) in delaying mitosis until DNA replication and error checking are complete.

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