bio 111 10.6 – Flashcards

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question
You are studying cell cycle progression in an early frog embryo. If you were to inject a protein synthesis inhibitor into a cell during S phase, where do you predict that the cells would arrest?
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G2
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What is separase?
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A protein that destroys cohesin through its protease activity.
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What would you expect to happen if the anaphase-promoting complex/cyclosome (APC/C) failed to ubiquitinate securin?
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The cohesin complex will persist, preventing the cell from entering anaphase.
question
You are leading a team of researchers at a pharmaceutical company. Your goal is to design drugs that help fight cancer. Specifically, you want to focus on drugs that bind to and inactivate certain proteins, thereby halting cell cycle progression. One of your team members suggests targeting the retinoblastoma (Rb) protein and inhibiting this protein. Will this approach be successful? Why or why not?
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This approach will not be successful. Rb is tumor-suppressor protein, and functions to inhibit the action of a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would essentially create the same situation as in as a cell that lacks both copies of the Rb gene. Lack of Rb activity would release the inhibition of cell cycle regulatory proteins, thereby promoting cell cycle progression, rather than halting it.
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Growth factor receptors are typically found in the
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cell membrane.
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If the protein retinoblastoma is ________, it can bind to and ________ the Myc protein.
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dephosphorylated ; inactivate
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The growth factors illustrated in this system are positive regulatory growth factors. Why are they considered 'positive' growth factors.
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They increase the rate of cell proliferation.
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How does myc become active?
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It dissociated from Rb.
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Mutations in the protein retinoblastoma (Rb) are often associated with cancer in the eye. What mutation might lead to cancer?
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A mutation that prevents Rb from becoming phosphorylated.
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The success of DNA replication is assessed during the ______ phase.
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g2
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The cell cycle is regulated by checkpoints during the _______ phases.
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G1, G2, and M
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A eukaryotic cell that receives a "go-ahead" signal at the G1 checkpoint of the cell cycle will
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complete the cycle and divide.
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A cell that is in an environment that has an abnormally low pH will NOT pass which checkpoint?
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G1
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DNA repair enzymes will be highly active during what phase of the cell cycle?
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G2
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The proteins ________ work together to free the transcription factor that is bound by the retinoblastoma protein.
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cyclin and cyclin dependent kinase
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Mutated forms of the Rb protein
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do not bind to E2F thereby promoting uncontrolled cell division.
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The protein ________ checks for damaged DNA, thereby acting as a "quality control" for the cell.
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p53
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What mutation would allow the cell to divide when it should not and could possibly lead to cancer?
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None of these will lead to cell proliferation.
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Which mutation would allow the cell to pass the G1 checkpoint when it should not?
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A mutation in Rb, preventing it from associating with E2F.
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A pregnant mother recently had an ultrasound that indicated massive defects in the formation of her unborn baby's heart. Other oddities were noted in the spinal cord region, the kidneys, and the formation of the facial features. She had an amniocentesis to examine the baby's karyology, and it was noted that there was a deletion of a small piece of one chromosome. The doctors advised her that her that she would likely miscarry. The devastated parents consult you as a genetic advisor on the likelihood that a future pregnancy would end similarly. What advise do you give this unfortunate couple?
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The mutation was probably a germ line mutation that only affected a single egg or sperm, so they should try to have more children
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A new small molecule drug inhibits the function of the APC/C. If this drug were applied to cells undergoing the cell cycle, what do you think would be the result? Check all that apply.
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Securin would not be destroyed in these cells. These cells would not be able to undergo Anaphase A. These cells would not be able to degrade mitotic cyclins. These cells would not be able to exit mitosis.
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Estimates are that p53 is mutated in 50% of all human cancers. If the gene that encodes p53 is mutated such that p53 is non-functional, what processes would be affected? Check all that apply.
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The ability to halt the cell cycle in response to DNA damage. The ability to repair DNA damage. The ability to stimulate cell death processes if the cell is irreparably damaged.
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The progress of the eukaryotic cell cycle is regulated primarily by what proteins?
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Cyclins
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You are examining the effect of maturation-promoting factor (MPF) in sea urchin cells, which have a diploid number of 36. If you fuse a dividing sea urchin cell with a G1 arrested oocyte, what would be the outcome?
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The G1 cell would enter mitosis, but would likely arrest at the spindle checkpoint because the chromosomes have not been properly replicated.
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