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BIO 320 (De Lozanne/ O Halloran) - Test 3 With
Complete Solutions
Cyclin-dependent kinases (Cdk) can be regulated by all of the following mechanisms EXCEPT: Binding of Cdk inhibitors Cyclin degradation Phosphorylation of the Cdk Cdk degradation Changes in Cyclin concentration - ANSWER Cdk Degradation
How is the synthesis of S-Cyclin stimulated? By the degradation of the E2F inhibitor By the activation of the transcription factor Rb protein G1/S-CDK inactivates the Rb protein by phosphorylation G1-CDK inactivates the E2F factor G1-CDK acts as a transcription factor for the S-Cyclin gene - ANSWER G1/S-CDK inactivates the Rb protein by phosphorylation
Which of the following is a CORRECT sequence of events necessary for entry into S-phase? Cdc6 is ubiquitylated by S-cdk, this causes firing of the origin of replication. Cdc6 is phosphorylated by S-cdk, then MCMs and ORC are recruited to the pre-Replicative complex (Pre-RC). Cdc6 binds to ORC, then MCMs bind the cdc6-ORC complex to form the Pre-RC. S-cdk is activated by the binding of E2F to the Pre-RC ORC is phosphorylated by S-cdk, then Cdc6 and MCMs bind to ORC to form the Pre-RC.
- ANSWER Cdc6 binds to ORC, then MCMs bind the cdc6-ORC complex to form the Pre-RC.
You fuse a cell in S-phase with one in M-phase. What would be a likely observation in this fused cell? The chromosomes of the cell in M phase will decondense. Non-phosphorylated condensins from the cell in S-phase will get phosphorylated. The chromosomes of the cell in M phase are induced to replicate again. Non-phosphorylated ORC from the cell in M-phase will get phosphorylated. Nothing happens to the chromosomes of either cell. - ANSWER Non-phosphorylated condensins from the cell in S-phase will get phosphorylated.
The function of Cohesins is to: Bind to the centromere and form the kinetochore. To condense a DNA chromatid by coiling DNA Adhere the kinetochore to the microtubules. Adhere two sister chromatids together. Bind to condensins on the chromosome. - ANSWER Adhere two sister chromatids together.
What would be the effect of artificially DECREASING the activity of CDC25 in the cell? The cell would grow smaller. The phosphorylation of Cdc25 would be delayed The cell cycle would get shorter. The activation of APC/Cdc20 would occur faster. The removal of inhibitory phosphates from S-Cdk would be delayed. - ANSWER The phosphorylation of Cdc25 would be delayed
During the G2 Checkpoint damage to DNA results in: The degradation of M-cyclin The activation of the M-Cdk specific CKI
prometaphase --- kinetochores - ANSWER prophase--- overlap microtubules
Which of the following statements applies to Anaphase B? The overlap microtubules elongate with the help of MAP proteins. Cytoplasmic dynein pulls the overlap microtubules toward the spindle poles. Catastrophins depolymerize the kinetochore microtubules. The kinetochore microtubules elongate with the help of MAP proteins Cytoplasmic dynein pulls the chromatids toward the spindle poles - ANSWER The overlap microtubules elongate with the help of MAP proteins.
Which of the following events marks the END of prophase? Dissasembly of the nuclear lamina. Cohesion of DNA by cohesin. Assembly of the nuclear envelope Condensation of DNA by condensin. Binding of microtubules to kinetochores. - ANSWER Dissasembly of the nuclear lamina.
Which of the following statements about kinetochores is FALSE? Kinetochores contain catastrophins to destabilize MT plus ends. Kinetochores contain cytoplasmic dynein Kinetochores assemble on the telomeric region of chromosomes. Kinetochores contain plus-end directed kinesin related motors. Kinetochores bind to microtubules without capping them - ANSWER Kinetochores assemble on the telomeric region of chromosomes.
Which of the following motor activities are important during prometaphase? (+)-directed Kinesin Related Protein (+KRP) are used to elongate the kinetochore microtubules.
When attached to the chromosome arms, Chromokinesin moves the chromosome to the middle of the spindle. When attached to overlap microtubules, (+)-directed Kinesin Related Protein (+KRP) moves chromosomes to the middle of the spindle. When attached to the kinetochore, Chromokinesin moves chromosomes to the middle of the spindle. When activated at the two kinetochores on a chromosome, Cytoplasmic dyneins move the chromosome to a spindle pole. - ANSWER When attached to the chromosome arms, Chromokinesin moves the chromosome to the middle of the spindle.
Which of the following statements about MAD2 is FALSE? The presence of MAD2 on kinetochores is sensitive to tension applied to the kinetochore. MAD2 is absent from kinetochores during Anaphase. The presence of MAD2 on the kinetochores produces a signal to activate APC. MAD2 is part of the Metaphase Checkpoint MAD2 is not found at the spindle poles. - ANSWER The presence of MAD2 on the kinetochores produces a signal to activate APC.
Which of the following events does NOT occur during the Metaphase to Anaphase Transition? APC adds ubiquitin to Cohesin. M-Cyclin is degraded. APC is activated by Cdc APC adds ubiquitin to M-Cyclin Cohesin is degraded. - ANSWER APC adds ubiquitin to Cohesin.
Which of the following proteins is never found at the kinetochore? Gamma-tubulin MAD
Rb - ANSWER Akt
Which of the following is NOT a typical event of intrinsic apoptosis? Transfer of phosphatidyl-serine (PS) to the exterior surface of the cell membrane. Activation of procaspases. Breakdown of the plasma membrane and release of cell contents. Fragmentation of DNA. Release of cytochrome C from the mitochondria. - ANSWER Breakdown of the plasma membrane and release of cell contents.
Binding of survival factors to their cell surface receptor will produce the following events EXCEPT for: Activation of a PI-3 kinase Production of PI(3,4,5,)P Activation of the protein BAD Phosphorylation of the protein PKB (Akt) Inhibition of procaspase activation - ANSWER Activation of the protein BAD
Which of the following is FALSE concerning Protein Kinase A (PKA)? PKA is activated when the regulatory subunit dissociates from the catalytic subunit PKA has regulatory subunits that bind cAMP PKA activation results in increased levels of cytoplasmic calcium PKA can enter the nucleus to phosphorylate Transcription Factors PKA can phosphorylate enzymes in the cytoplasm - ANSWER PKA activation results in increased levels of cytoplasmic calcium
Protein Kinase C is activated by: Calcium and diacylglycerol
Cyclic AMP bound to the catalytic subunits Cyclic AMP bound to the regulatory subunits Calcium and Ip Binding of GTP - ANSWER Calcium and diacylglycerol
G-protein Receptor signaling can result in all of the following changes EXCEPT: Activation of Protein Kinase B (Akt) Activation of Protein Kinase C Activation of Phospholipase C Activation of CamKinaseII Activation of Protein Kinase A - ANSWER Activation of Protein Kinase B (Akt)
Which of the following statements about IP3 is TRUE? IP3 binds to Protein kinase C to release the regulatory subunit IP3 is stored within the Endoplasmic reticulum IP3 binds to calcium channels on the Endoplasmic Reticulum IP3 binds to phosphoinositides IP3 binds to and activates CaM-Kinase - ANSWER IP3 binds to calcium channels on the Endoplasmic Reticulum
Which of the following would result in a DECREASE in the activity of CaM-kinase II? Binding of Calcium/calmodulin to CaM-kinaseII Auto-phosphorylation of CaM-Kinase II A genetic mutation that deletes the gene for the protein phosphatase for CaM-kinase II. Release of calmodulin from phosphorylated CaM-kinase II Release of the catalytic domain of CaM-Kinase II from the inhibitory domain - ANSWER Release of calmodulin from phosphorylated CaM-kinase II
The diagram below shows an important signaling pathway that involves multiple proteins.
A) Identify protein labeled "B"
B) Protein "B" is bound to protein "A" by a special domain indicated by the arrow "C". What type of domain is this?
C) Proteins "D" and "E" are recruited to the membrane when the pathway is activated. What type of domain do they use to bind to lipids on the membrane?
D) Activation of protein "D" produces two effects: It can inhibit caspase activity and it can also phosphorylate protein "E". In turn, phosphorylated protein "E" triggers a chain of events that lead to the inhibition of cytochrome release from mitochondria. What biological process is regulated by this signaling pathway?
E) To test the sequence of events in this pathway you introduce into a cell a large number of the protein "E" domains as shown by arrow "F". Explain in detail what steps of this pathway will occur normally in thi - ANSWER A) PI3 Kinase
B) SH2 or PTB on a phosotyrosine
C) PH to inotisol phospholipase
D) Apoptosis
E) everything downstream of binding the PH domain, so cytochrome will not be released, and caspase activity will not be inhibited, and apoptosis will occur
Order the following events in animal cell division:
A. Alignment of chromosomes at the spindle equator.
B. Attachment of microtubules to chromosomes.
C. Breakdown of nuclear envelope.
D. Condensation of chromosomes.
E. Decondensation of chromosomes.
F. Duplication of centrosome.
G. Elongation of the spindle.
H. Pinching of cell in two.
I. Re-formation of nuclear envelope.
J. Separation of centrosomes.
K. Separation of sister chromatids. - ANSWER The events occur in the following order: duplication of the centrosome (F), separation of centrosomes (J), condensation of chromosomes (D), breakdown of nuclear envelope (C), attachment of microtubules to chromosomes (B), alignment of chromosomes at the spindle equator (A), separation of sister chromatids (K), elongation of the spindle (G), re-formation of nuclear envelope (I), decondensation of chromosomes (E), and pinching of cell in two (H).
Consider the events that lead to formation of the new nucleus at telophase. How do
Explain why Mad2-deficient cells live in the absence of benomyl but die in its presence. - ANSWER In the absence of benomyl, the majority of spindles form normally and the spindle-attachment checkpoint plays no role. As a consequence, Mad2 is irrelevant. In the presence of benomyl, however, cells that are defective for Mad2 cannot stop cell-cycle progression, with the result that chromosomes are segregated incorrectly, causing the cells to die.
Both sister chromatids of a chromosome occasionally end up in one daughter cell.
a) Suggest one possible cause for such an event. How could such a thing happen?
b) What would be the consequences for the daughter cells if this event occurred in mitosis? - ANSWER A)
- If the microtubules or their connections with a kinetochore were to break during anaphase, - If microtubules from the same spindle pole attached to both kinetochores,
- If the cohesins that link sister chromatids were not degraded,
- If a chromosome never engaged microtubules, and was left out of the spindle, (Should be corrected at the M- Anaphase checkpoint)
B) Apoptosis
Protein that binds to a GTP-binding protein and activates it by stimulating release of tightly bound GDP, thereby allowing it to bind GTP. - ANSWER Guanine Nucleotide Exchange Factor (GEF)
The small molecule MG132 is a commercial inhibitor of the proteasome that can rapidly diffuse through the plasma membrane and completely blocks proteasome activity. You add this drug to cells that are in late G2. A control sample of untreated cells enter M-phase within 5 minutes. What do you think will be the effect of treating the cells with MG132 in regard to the following events? For EACH EVENT, explain: (1) why the drug would or would not affect that event and (2) by which mechanism. In addition, for each event, (3) describe which specific proteins will be affected by the inhibition of the proteasome and (4) how the effect on those proteins will change the particular event of the cell cycle. BE EXPLICIT!
A) Spindle assembly
B) Chromosome capture by microtubules
C) Chromatid separation
D) Spindle elongation - ANSWER a) Spindle assembly MG132 will not affect spindle assemble. Protein degradation is not a requirement for spindle assembly. (For example, the phosphorylation of nuclear lamins leads to fragmentation (but not degradation) of the nuclear envelope. This process is reversible, and dephosphorylation of lamins results in fusion of nuclear envelope fragments in telophase.) b) Chromosome capture by microtubules MG132 will not affect chromosome capture. Protein degradation is not required for chromosome capture by microtubules or microtubule dynamics. c) Chromatid separation MG132 will block chromatid separation. Normally, APC/C ubiquitinates securin, targeting it for degradation in the proteasome. Thus, securin will not be degraded in the presence of MG132. This would cause securin to remain bound to separase, keeping separase in an inactive state. Inactive separase cannot cleave cohesin, resulting in an inhibition of chromatid separation. d) Spindle elongation MG will block spindle elongation Spindle elongation occurs in Anaphase. M-cyclin is degraded during the metaphase-anaphase transition. MG132 will block proteasome degradation of M-cyclin. As a result, the cell will not enter into anaphase (resulting in metaphase arrest) and the spindle will not elongate.
General term for a protein that binds a specific extracellular molecule (ligand) and initiates a response in the cell - ANSWER Receptor
Alteration of sensitivity following repeated stimulation, reducing a cell's response to that level of stimulus - ANSWER Adaptation (desensitization)
Compact protein module that binds to a particular structural motif in another protein (or lipid) molecule with which the signaling protein interacts - ANSWER Interaction domain
A signal relay chain involving multiple protein kinases, each of which is activated by phosphorylation and then phosphorylates - ANSWER Kinase Cascade
Protein kinase whose activity is regulated by the binding of Ca++activated calmodulin, and which indirectly mediates the effects of Ca++ by phosphorylation of other proteins - ANSWER CAM II Kinase
Cell-surface receptor that when activated by ligand binding adds phosphates from ATP to tyrosine side chains in its own cytoplasmic domain - ANSWER Receptor Tyrosine Kinase (RTK)
A kinase that is involved in intracellular signaling pathways activated by cell-surface receptors and that phosphorylates inositol phospholipids at the 3 position of the inositol ring. - ANSWER PI3 Kinase
A protein domain that binds to a short amino acid sequence containing a phosphotyrosine - ANSWER SH2 and PTB
Protein domain that binds to specific amino acid sequences that contain a lot of pralines
Protein domain that binds to a specific phosphorylated phospholipid like PI(4,5)P2 - ANSWER PH
What would happen if you fused together two cells, one in G1-phase and one in M-phase A) The nucleus of the cell in G1 will start DNA replication B) The nucleus of the cell in G1 will enter M-phase C) The nucleus of the cell in M-phase will enter G1-phase D) The nucleus of the cell in M-phase will start DNA replication E) The two nuclei will keep going through their respective phases of the cell cycle - ANSWER B) The nucleus of the cell in G1 will enter M-phase - because mCDK will be present
What would happen if a cell did not have Wee1?
M-Cdk would not be activated M-cyclin would not be synthesized M-cyclin would not be phosphorylated The activity of M-Cdk would rise proportionally to the synthesis of M-cyclin E) M-Cdk would be phosphorylated by CAK but it would not trigger entry into M-phase - ANSWER The activity of M-Cdk would rise proportionally to the synthesis of M-cyclin - because CAK would still phosphorylate the active site, while Wee1 would be unable to inhibit the activity
What statement is wrong based on Figure 17-16? A) There is a specific cyclin for each phase of the cell cycle B) All cyclins bind to a CDK protein C) All CDK proteins are inactive if they don't have a cyclin bound to them D) All cyclins are destroyed at some point of the cell cycle E) There are times in the cell cycle when there are NO cyclin proteins present - ANSWER A) There is a specific cyclin for each phase of the cell cycle - because not all phases have cyclins associated, or some have multiple occuring at certain times
What would be the effect of having a reduced amount of Rb protein in a cell? G1-Cdk would not be active S-Cdk would not be activated G1/S cyclin would not be synthesized The cell would enter S-phase prematurely The E2F factor would be inactivated - ANSWER The cell would enter S-phase prematurely
- because E2F would be present to synthesize G1/S cyclin and S cyclin
What would be the effect of making a mutant of Cdc- 6 protein that cannot be phosphorylated? Cdc-6 would not bind to ORC
know how much do Homework #8) You add caffeine to a normal healthy cell that is in G2. What is likely to happen? The cell will go back to S phase The cell will stop in G The cell will continue to M phase The cell will stop in M phase The cell will die - ANSWER The cell will continue to M phase - there is nothing stopping it
Imagine you can increase the activity of particular motors in the spindle. Which motor would you increase to make the spindle shorter? Chromokinesin Dynein at cell cortex KRP (+) on overlap MTs KRP (-) on overlap MTs Kinetochore KRP - ANSWER KRP (-) on overlap MTs
Which of the following is FALSE about Gprotein coupled receptor signaling? A. Receptors never leave the plasma membrane B. Receptors have 7 transmembrane domains C. Receptors interact with a trimeric G-protein complex D. The trimeric G-protein complex is on the plasma membrane E. The trimeric G-protein complex sends out cAMP - ANSWER E. The trimeric G-protein complex sends out cAMP - cAMP is the secondary signal from Adenylyl Cyclase which is an effector for the Trimeric G-protein
What is the GEF in G-protein coupled receptor signaling? A. There is no GEF B. The G-alpha subunit C. The G-beta subunit
D. The G-gamma subunit E. The G-Protein coupled receptor - ANSWER E. The G-Protein coupled receptor
Which of the following is TRUE about a cell that has returned to resting state (no signaling)? A) G-alpha-s is bound to GTP B) G-alpha-i is bound to GTP - even though it's an inhibitor of a signal, it is still in a signaling state, not a resting state C) Adenylyl cyclase is bound to GDP D) cAMP has been degraded in the cytosol E) Calcium levels are high in the cytosol - state of signaling also - ANSWER D) cAMP has been degraded in the cytosol
IP3 raises calcium concentration in the cytoplasm. Where does the calcium come from? A)The Endoplasmic reticulum B)Mitochondria C)Outside of the cell D)The nucleus E) The cell synthesizes more calcium - ANSWER A)The Endoplasmic reticulum
What would happen to the Insulin Signaling Pathway if you overexpressed the SH domain of Grb2? SOS would not bind phosphoinositide docking sites Decreased phosphorylation of insulin receptor The scaffolding protein would not be linked to IRS IRS1 would not bind the insulin receptor Decreased Phosphorylation of the GDP of ras - ANSWER The scaffolding protein would not be linked to IRS
