SMC Proteins and Chromosome Structures Quiz
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Questions and Answers

What is the primary role of the cohesin proteins in eukaryotic cells?

  • To regulate the ON and STOP switches for cell division
  • To link together sister chromatids after replication and keep them together during chromosome condensation (correct)
  • To maintain the condensed structure of chromosomes during mitosis
  • To induce positive supercoiling in DNA during chromosome condensation
  • How do the condensin proteins affect the structure of DNA when they bind to it?

  • They cause the DNA to become underwound
  • They have no effect on the DNA's supercoiling
  • They create positive supercoils in the DNA, causing it to become overwound (correct)
  • They induce negative supercoiling in the DNA
  • Which of the following is NOT a key transition point in the eukaryotic cell cycle?

  • The point where sister chromatids are segregated during cell division
  • The point where chromosomes condense as cells enter mitosis (correct)
  • The ON switch, where a cut or break in tissue causes cells to grow rapidly
  • The STOP switch, where cells stop growing when they bump into each other
  • Which of the following statements about SMC proteins is true?

    <p>SMC proteins are a class of chromatin proteins, in addition to histones and topoisomerases</p> Signup and view all the answers

    What is the main function of the condensin proteins in eukaryotic cells?

    <p>To maintain the condensed structure of chromosomes during mitosis</p> Signup and view all the answers

    Which of the following cell types are most likely to rarely or never divide?

    <p>Nervous and heart cells</p> Signup and view all the answers

    What are the red bars indicating in the eukaryotic cell cycle?

    <p>Points where the cell can exit and enter a nondividing state</p> Signup and view all the answers

    What are cyclins in relation to the cell cycle regulation?

    <p>Proteins regulating the timing of the cell cycle</p> Signup and view all the answers

    What are internal regulators in the cell cycle control process?

    <p>Respond to events inside the cell</p> Signup and view all the answers

    What is the consequence of uncontrolled cell growth as mentioned in the text?

    <p>Cells invade other normal cells' space</p> Signup and view all the answers

    What is a characteristic of a benign tumor mentioned in the text?

    <p>Responds to 'stop' signals</p> Signup and view all the answers

    How does apoptosis relate to uncontrolled cell growth?

    <p>Results in programmed cell death</p> Signup and view all the answers

    What triggers the activation of the gene coding for the p21 protein?

    <p>Phosphorylated p53 protein accumulation</p> Signup and view all the answers

    Which protein promotes apoptosis by binding to and blocking the action of the apoptosis inhibitor Bcl-2?

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

    What is the main protein destruction machine in a cell?

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

    What happens when the DNA damage cannot be repaired and p53 is activated?

    <p>Genes encoding proteins that trigger cell death by apoptosis are activated</p> Signup and view all the answers

    Which event leads to cell cycle arrest at the restriction point?

    <p>Inhibition of Cdk-cyclin by p21 protein</p> Signup and view all the answers

    What role does the Rb protein play in cell cycle control?

    <p>It binds to E2F and prevents it from activating transcription of genes required for DNA replication</p> Signup and view all the answers

    What event triggers the onset of S phase in cells stimulated by growth factors?

    <p>Activation of the Ras pathway and subsequent phosphorylation of the Rb protein</p> Signup and view all the answers

    What happens to the Rb protein during M phase?

    <p>It is dephosphorylated so that it can once again inhibit E2F</p> Signup and view all the answers

    What event leads to the activation of checkpoint kinases and subsequent phosphorylation of the p53 protein?

    <p>Damaged DNA</p> Signup and view all the answers

    What is the role of the E2F transcription factor in cell cycle control?

    <p>It activates the transcription of genes coding for proteins required for DNA replication when not bound to the Rb protein</p> Signup and view all the answers

    What is the role of the G1 Cdk-cyclin complex in cell cycle control?

    <p>It phosphorylates the Rb protein, causing it to dissociate from E2F and allow gene transcription</p> Signup and view all the answers

    What is the primary role of the Mdm2 protein in relation to p53?

    <p>It marks p53 for degradation</p> Signup and view all the answers

    How does the accumulation of phosphorylated p53 lead to cell cycle arrest?

    <p>It activates the transcription of the p21 gene, which inhibits Cdk-cyclin complexes</p> Signup and view all the answers

    What is the role of the Puma protein in the p53 pathway?

    <p>It promotes apoptosis by binding to and blocking the action of Bcl-2</p> Signup and view all the answers

    Which of the following protein kinases is responsible for initiating the p53 response to DNA damage?

    <p>ATM or ATR</p> Signup and view all the answers

    What is the consequence of the inhibition of Cdk-cyclin complexes by p21?

    <p>It prevents the phosphorylation of the Rb protein, leading to cell cycle arrest</p> Signup and view all the answers

    What is the primary function of the Bcl-2 protein in the p53 pathway?

    <p>It inhibits apoptosis by blocking the action of Puma</p> Signup and view all the answers

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