Exam 4 SG. Mair. Cell Cycle

These chromosome spreads from cells arrested in prometaphase were stained for cohesins and condensins; CREST labels the kinetochore. Indicate which image (1 or 2) corresponds best to the localization of the following proteins. Scc1 Smc2 CAP-H Scc3 *insert image*

1 1 2 1

Indicate which boxed region (1, 2, or 3) in the FACS plot below corresponds better to each of the following phases of the cell cycle. Your answer would be a three-digit number composed of numbers 1 to 3, with each number used once, e.g. 312. (1) G1 phase (3) S phase (2) G2 and M phases *insert image*

1, 3, 2

You add the drug fucoxanthin to cell cultures. Fucoxanthin is known to induce cell-cycle arrest in G1. After one day, you add the thymidine analog BrdU to the culture media, collect the cells after an hour, treat them with anti-BrdU antibody and the fluorescent DNA stain DAPI, and finally subject them to fluorescence-activated cell sorting (FACS). The FACS data can be viewed as a two-dimensional dot plot composed of thousands of dots, in which each cell is represented by one dot at coordinates that correspond to the intensities of the DAPI fluorescence signal (X axis) and BrdU fluorescence signal (Y axis) for that cell. Indicate which boxed region (1, 2, or 3) in the FACS plots corresponds better to each of the following phases of the cell cycle. Your answer would be a three-digit number composed of numbers 1 to 3, with each number used once, e.g. 312. G1 phase S phase G2 and M phases *insert image*

2 1 3

Which of the following simplified diagrams better shows the changes in the concentrations of three major cyclin-Cdk complexes (G1/S-Cdk, S-Cdk, and M-Cdk) in the cell in different stages of the cell cycle? **insert image somehow**

A

Consider two mammalian cells, one in G1 and the other in G0 (stationary) phase. If they are stimulated to pass the restriction point by the addition of an extracellular proliferation signal, but the signal is then immediately removed, what would you expect to happen? A. Both cells will replicate their DNA. B. Only the G1 cell will replicate its DNA. C. Only the G0 cell will replicate its DNA. D. Only the G1 cell will start to replicate its DNA, but will stop halfway through the replication and will not reach G2. E. Neither of the cells will replicate their DNA.

A. Both cells will replicate their DNA.

Which of the following is more directly driven by active M-Cdk? A. Centrosome maturation B. Centrosome duplication C. Nuclear envelope reassembly D. Inactivation of APC/C E. Cell cleavage

A. Centrosome maturation

During meiosis, sister chromatids within a bivalent are held together by a complex containing the unique meiotic cohesin: A. Rec8 B. SMC1 C. Scc1 D. SCP2 E. SCP1

A. Rec8

Mutant Saccharomyces cerevisiae cells that lack the gene encoding securin can divide more or less normally by mitosis, without significant chromosome segregation defects. Cells harboring a nondegradable version of securin, on the other hand, arrest in metaphase as expected, since they cannot activate separase to enter anaphase. Similarly, cells lacking Cdc20 arrest in metaphase, since they cannot activate APC/C. Finally, cells lacking both securin and Cdc20 arrest in anaphase: they manage to separate sister chromatids, but do not progress much further. These results suggest that in wild-type cells, ... A. degradation of securin is necessary to trigger sister-chromatid separation. B. degradation of securin is sufficient to trigger sister-chromatid separation. C. Cdc20-APC/C is NOT necessary for sister-chromatid separation. D. Cdc20-APC/C is NOT necessary for later events in anaphase. E. All of the above.

A. degradation of securin is necessary to trigger sister-chromatid separation

APC/C-CDC20 triggered proteolysis of securin, cyclin A and cyclin B occur during: A. metaphase-to-anaphase transition B. cell cycle entry C. mitosis. D. DNA synthesis. E. G2/M transtition.

A. metaphase-to-anaphase transition

Ubiquitylation of securin is required for: A. Separase activation and Scc1 cleavage B. APC/C activation and M-cyclin degradation. C. APC/C activation and sister chromatid separation. D. SCF activation and sister chromatid separation. E. Separase activation and cohesion removal.

A. separase activation and Scc1 cleavage

Which of the following events contribute to an 'anaphase-wait' signal during the spindle assembly checkpoint? A. syntelic and monotelic spindle attachments B. Recruitment of the mitotic checkpoint complex MCC C. dephosphorylation of unattached kinetochore protein D. chromosome alignment at the spindle equator E. inhibition of APC/C-CDC20

A. synthetic and monotelic spindle attachments B. recruitment of the mitotic checkpoint complex MCC E. inhibition of APC/C-CDC20

Which one of the following statements describes meiosis correctly? Cytokinesis I produces haploid cells. Sister chromatids are segregated during anaphase II. Pairs of homologous chromosomes contain a pair of sister chromatids each. A bivalent is a four chromatid structure. All of the above.

All of the above

Inactivation of cohesion (A), condensin (B) or separase (C) can result in: - unresolved sister chromatids - diplochromsomes; re-replicated non-disjoined chromatids - precocious sister chromatid separation

B C A

In the following schematic diagram of a typical eukaryotic cell cycle, choose two major time points (among A to E) at which the cell-cycle control system normally arrests the cycle if DNA damage is detected. Your answer would be a two-letter string composed of letters A to E only in alphabetical order, e.g. CE. *insert picture*

B C

The following schematic diagram shows the activation of M-Cdk in mitosis. Indicate which proteins below correspond to those indicated as A to D in the diagram. Your answer would be a four-letter string composed of letters A to D only, e.g. BACD. Wee1 CAK Cdc25 M-cyclin *insert image*

B C D A

In the fission yeast Schizosaccharomyces pombe, the proteins Cut1 and Cut2 form a complex that is catalytically inactive. At the onset of anaphase, Cut2 is polyubiquitylated by a large E3 complex containing Cut4, Cut9, Cut23, and other proteins, and is subsequently destroyed. Cut1 then cleaves Rad21, a non-SMC component of a complex that also contains two SMC proteins, thus allowing sister-chromatid separation. Mutations in the cut genes lead to the cut phenotype, in which the cell attempts cytokinesis without chromosome segregation. Indicate which of the following proteins or protein complexes corresponds to or contains the product of the genes cut1 (A), cut2 (B), cut4 (C), and rad21 (D). Your answer would be a four-letter string composed of letters A to D only, e.g. DCAB. Securin Cohesin Anaphase-promoting complex Separase

B D C A

In most mammalian cells, low M-cyclin protein levels are maintained during G1 phase. What is mainly responsible for maintaining these low levels? A. Cdc20-APC/C B. Cdh1-APC/C C. Skp2-SCF D. β-trCP-SCF E. p27

B. Cdh1-APC/C

Sort the following schematic diagrams (A to F) to reflect the order of events in a typical eukaryotic M phase. An interphase cell in G2 phase is drawn on the left for comparison. Your answer would be a six-letter string composed of letters A to F only, e.g. BCEADF. **insert image somehow**

C, F, E, D, A, B

Loss of the gene encoding shugoshin in many multicellular organisms leads to sterility, suggesting defects in meiosis. What would you expect to occur in meiotic cells lacking shugoshin? A. The homologs fail to separate in anaphase I. B. The sister chromatids fail to separate in anaphase II. C. All chromatids separate prematurely in anaphase I. D. Removal of cohesion between homolog arms fails in prophase I. E. Removal of cohesion between sister chromatids fails in prophase II.

C. All chromatids separate prematurely in anaphase I

Sister chromatid segregation during mitosis requires destruction of the cohesion ring to allow sister chromatid separation. Which cohesion protein is degraded? And which protease is directly required for its degradation? A. Rec8 and separase B. Scc1 and securin C. Scc1 and separase D. SMC1 and APC/C E. CAP-G and securin

C. Scc1 and separase

A cell has been subjected to ultraviolet irradiation, causing a significant number of mutations in the genome. Which of the following would you NOT expect to occur as a result? A. Activation of the protein kinase ATR B. Activation of the protein kinase Chk1 C. Inactivation of the protein phosphatase Cdc25 D. Binding of p53 to Mdm2 E. Stabilization of p53

D. Binding of p53 to Mdm2

Which of the following events occurs in mitotic metaphase? (prometaphase) A. Nuclear envelope breakdown B. Nuclear envelope reassembly C. Chromosome attachment to spindle microtubules for the first time D. Chromosome alignment at the spindle equator E. Mitotic spindle assembly

D. Chromosome alignment at the spindle equator

Which of the following proteins is the product of an immediate early gene expressed following mitogenic stimulation of cell-cycle entry? A. E2F B. Rb C. Myc D. G1-cyclins E. All of the above

D. G1-cyclins

Which division in meiosis is more similar to mitosis? In which division do sister chromatids separate from each other? A. Meiosis I; meiosis I B. Meiosis I; meiosis II C. Meiosis II; meiosis I D. Meiosis II; meiosis II

D. Meiosis II; meiosis II

If cells that have started mitosis are treated with nocodazole, a drug that depolymerizes microtubules, what would you expect to happen? Where would you expect MCC (mitotic checkpoint complex) protein Mad2 to be localized? A. The cells would arrest in prometaphase; Mad2 would be localized to the spindle poles. B. The cells would arrest in telophase; Mad2 would be localized to the spindle poles. C. The cells would immediately enter anaphase, finish mitosis, and enter G1; Mad2 would be localized to the spindle poles. D. The cells would arrest in prometaphase; Mad2 would be localized to almost all kinetochores. E. The cells would arrest in telophase; Mad2 would be localized to almost all kinetochores.

D. The cells would arrest in prometaphase; Mad2 would be localized to almost all kinetochores

The cell cycle can be arrested in mitosis when a single sister-chromatid pair is mono-oriented on the mitotic spindle. If at this point a glass microneedle is used to pull the mono-oriented chromosome toward the pole to which it is not attached, the cell proceeds to anaphase. This observation confirms that ... A. mono-oriented chromosomes are stable. B. mechanical tension drives the formation of bi-oriented chromosomes. C. bi-oriented chromosomes activate the spindle assembly checkpoint. D. lack of mechanical tension at the kinetochore in at least one chromosome prevents entry into anaphase. E. mechanical tension at the kinetochore in at least one chromosome is required for entry into anaphase.

D. lack of mechanical tension at the kinetochore in at least one chromosome prevents entry into anaphase

Indicate true (T) and false (F); your answer would be a five-letter string composed of letters T and F only, e.g. TFTFF. The amino acid motifs RXL and KXL in the C-terminus of retinoblastoma act as putative ... Cdk phosphorylation sites. Dimerization domains. Cyclin binding sites. DNA binding domains. Transcription regulators.

T F T F F

Which of the time points (A to E) n the following schematic drawing of the mammalian cell cycle represents the spindle assembly checkpoint? **insert image**

E

How is centrosome duplication similar to DNA replication? A. They both use a semiconservative mechanism. B. They are initiated at around the same time in the cell cycle, near the G1/S transition. C. They are both controlled in such a way that they replicate once and only once per cell cycle. D. They are both separated from their sister copies in mitosis. E. All of the above.

E. All of the above

Which of the following events contributes to driving the mammalian cell past the restriction point of the cell cycle? A. Phosphorylation of Cdh1-APC/C by G1/S-Cdk B. Destruction of CKIs that target S-Cdks C. Phosphorylation of Rb by G1-Cdk, G1/S-Cdk, and S-Cdk D. Activation of E2F gene expression by active E2F protein E. All of the above

E. All of the above

Retinoblastoma is a so-called pocket protein and a key target for CDK-cyclin phosphorylation. This affects its binding affinity for the transcription factor ________ and regulates _________ gene transcription. P53, DNA repair E2F, S-phase Myc; S-phase

E2F, S-phase

Indicate true (T) and false (F); your answer would be a five-letter string composed of letters T and F only, e.g. TFTFF. The anaphase promoting complex catalyzes ubiquitylation of regulatory proteins involved in exit from mitosis. APC/C is regulated by the association with: CAK. CDC25. Cdh1. CDC20. Cdt1.

F F F T F

Indicate true (T) and false (F); your answer would be a five-letter string composed of letters T and F only, e.g. TFTFF. During synapsis, the synaptonemal complex forms between: sister chromatids. chromatin. homologous chromosomes. centrioles. centromeres.

F F T F F

Indicate true (T) and false (F) statements below regarding meiosis in eukaryotic cells. Your answer would be a four-letter string composed of letters T and F only, e.g. TFFF. Bivalents form before prophase I. Crossing-over begins before the synaptonemal complex assembly. Chiasmata can first be seen under the microscope after the disassembly of the synaptonemal complexes. All recombination events lead to crossovers.

F T T F

Kinases transfer a phosphate group from ATP to a substrate protein; phosphorylation can enhance the activity of a protein. This is the case for Wee1 kinase. True False

FALSE Wee1 kinase phosphorylates Cdk and inactivates it

Phosphatases remove phosphate groups from proteins; this can decrease the activity of a protein. This is the case for CDC25 in Cdk regulation. True False

FALSE; Cdk is ACTIVATED when it loses a phosphate group by CDC25 phosphorylation

Indicate whether each of the following descriptions better applies to mitogens (M), growth factors (G), or survival factors (S). Your answer would be a four-letter string composed of letters M, G, or S only, e.g. GMSG. They promote cell-cycle progression They suppress apoptosis They trigger a wave of G1/S-Cdk activity They inhibit the degradation of cellular macromolecules

M S M G

Which of the following proteins are involved in Cdk activation. Indicate true (T) and false (F); your answer would be a four-letter string composed of letters T and F only, e.g. TFFF. CAK. Wee1. CDC20. CDC25.

T F F T

Which of the following proteins maintain sister chromatid cohesion during meiosis I. Indicate true (T) and false (F); your answer would be a four-letter string composed of letters T and F only, e.g. TFTFF. Rec8. shugoshin. separase. securin. phosphatase PP2A.

T T F F T

Indicate whether each of the following descriptions better applies to a Wee1 protein (W) or a Cdc25 protein (C). Your answer would be a four-letter string composed of letters W and C only, e.g. WWCW. It is a protein kinase. It activates M-Cdk complexes. It is a phosphatase. Its loss in fission yeast results in small cell size.

W C C W

In a multicellular organism such as a mammal, loss-of-function mutations in many genes can contribute to the development of cancer. These genes are therefore called tumor suppressors. In their absence, the cell fails to stop progression through the cell cycle under conditions in which normal cells would arrest, paving the way for tumorigenesis. Indicate whether each of the following proteins is (Y) or is not (N) expected to be the product of a tumor suppressor gene based on its function in the cell cycle. Your answer would be a four-letter string composed of letters Y and N only, e.g. YNNN. Rb Myc p53 p21

Y N Y Y

The separation of sister chromatids during ________ requires the destruction of cohesins by the enzyme ___________. Metaphase - securin Anaphase - separase Telophase - phosphatase 2A

anaphase - separase

When DNA is damaged, various protein _______ are recruited to the site of damage. The ________ MDM2 normally binds to p53 and promotes its ________ and degradation. _______ of p53 blocks binding to MDM2, allowing it to stimulate the ________ of numerous genes in the nucleus, including the Cdk inhibitor ________ which binds and inactivates Cdk-cyclin complexes to induce cell cycle arrest. One entry per blank space. More options provided than blank spaces.

kinase E3 ligase ubiquitylation phosphorylation transcription p21

"The ________________ is a large structure formed at the centromeric region of each eukaryotic chromosome. It captures spindle microtubules in mitosis, and therefore serves to attach the chromosomes to the spindle poles."

kinetochore

During mitogen-stimulated cell cycle entry, increased expression of the immediate early response gene __________ leads to increased ___________ levels. This triggers the ________ of the tumor suppressor __________ and its reduced binding to the transcription factor _______, which becomes free to stimulate the expression of ________ genes.

myc G1-Cdk phosphorylation retinoblastoma/Rb E2F S-phase

Activation of E2F requires the _________ of __________ by __________. Phosphorylation; myc; CDK activating kinase Inhibition; Cdk; Wee1 kinase Dephosphorylation; retinoblastoma; CDC25 Phosphorylation; retinoblastoma; cyclin-Cdk

phosphorylation; myc; CDK activating kinase