lecture questions

• ​Which of the following would most likely lead to activation of the EGFR signaling pathway?

  Activation of Ras-GEF.
• A mutant yeast strain stops proliferating when shifted from 25°C to 37°C. When these cells are analyzed at the two different temperatures, using a machine that sorts cells according to the amount of DNA they contain, the graphs below are obtained. In which stage of the cell cycle are the cells arrested when exposed to 37°C? Which of the following would explain the results of the mutant yeast strain?

  • G1 phase
  • It cannot activate proteins needed to enter S phase at 37°C.

  
• Which of the following would occur if a cell had a loss-of-function mutation at the Wee1 gene?

  The activity of M-Cdk would rise proportionally to the synthesis of M-cyclin.
• In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?

  At the end of G2 phase.
• Which of the following statements regarding the figure below is false?

  There is a specific cyclin for each phase of the cell cycle.

  
• Which of the following would be a consequence of having loss-of-function mutations at the gene that encodes the Rb protein?

  Cell would enter S phase prematurely.
• Which of the following statements regarding the S phase is false?

  The loading of the origin recognition complexes (ORCs) is triggered by S-Cdk.
• Which of the following describes a likely consequence of a eukaryotic cell expressing a mutated Cdc6 protein that cannot be phosphorylated?


  Cdc6 tries to bind to ORC during S phase.
• A chemical inhibitor of the proteasome is added to cells that have entered prophase. Which of the following is a likely consequence of this treatment?

  Replicated chromosomes will fail to separate.
• When a cell receives an apoptotic signal ___________ activate(s) __________ to destroy different types of biological molecules inside the cell.

  initiator caspases; executioner caspases
• Which of the following statements regarding apoptosis is true?


  The release of cytochrome c activates a caspase.
• Which of the following statements regarding p53 is false?

  • p53 is constantly expressed and is not regulated at the transcriptional level.

  p53 subunits always bind to other p53 subunits.

  p53 is activated when there is DNA damage.

  p53 regulates the cell cycle and apoptosis.

  All the above statements are true.
• Among the following cancers, one is currently leading in the number of deaths in the United States and in the rest of the world. In the United States, it contributes to cancer mortality more than the next three killing cancers combined. Worldwide, it claims more than 1.5 million lives every year. Which cancer is this?

  Lung cancer
• Which of the following genetic changes can convert a proto-oncogene into an oncogene?

  Amplification of the number of copies of the gene, causing overproduction of the protein.
• Which of the following statements regarding germline mutations is false?


  Germline mutations are typically caused by environmental factors.
• Which of the statements regarding the Rous sarcoma virus (RSV) is false?


  RSV can cause cancer in humans.
• Which of the following genetic alterations is associated with cancer?


  Gain-of-function mutation at G1 cyclin gene.
• Which of the following statements regarding Ras mutations in cancer patients is false?

  Oncogenic mutations usually result in higher levels of GDP-bound Ras.
• Which of the following statements is false?

  Loss-of-function mutations at Mdm2 promotes cancer.
• Which of the following steps in regulation of p53 happens last?

  p53 binds to the Mdm2 protein.
• Which of the following steps in epidermal growth factor signaling happens first?

  Autophosphorylation