In the following study, the investigators wanted to determine the role of cyclin Bin controlling the cell cycle. Earlier researchers had found that extracts madefrom frog eggs (Xenopus) contained all the necessary proteins and machineryrequired for DNA replication. This included proteins that regulated the mitosispromoting factor (MPF). At the time of this study, cyclin B was show to affect MPFactivity and the research group wanted to test using Xenopus egg extract in anassay. In Figure 1 (a) MPF activity was tested for its ability to phosphorylateHistone (H1) in sperm chromatin over a certain period of time. Additionally, thecyclin B concentration in the extract was measured.In figure 1b, the extract was tested after treatment with RNase which degradedonly the mRNA and not RNA or FRNA in the extract. Knowing that cyclin B is ashort-lived protein, why do you suppose the graph shows the results you see infigure 1b? Untreated extract(b) RNase-treated axtractMitotic events-- MPF activity- Cyclin B coneSpermchromatinTimeTime >RNase-treated extract + wild-type cyclin B MRNA(d) RNase-treated extract + nondegradable cyclin B MRNAMitotic eventsSpermchromatinTimeMitotic arrestTime >IGURE 13-7 Experimental demonstration that thethesis and degradation of cyclin B are required for theing of MPF activity and mitotic events in Xenopus eggacts. In all cases, MPF activity and cyclin B concentrationa determined at various times after addition of spermmatin to an extract treated as indicatod. Microscopicvations detorminod the occurrence of early mitotic events(blue shading), including chromosome condensation and nuclearenvelope breakdown, and of late events (orange shading).including chromosome decondensation and nuclear envelopereformation. Soe text for discussion. ISee A. W. Murray et al, 1989,Nature 339:275; adapted from A. Murray and T, Hunt, 1993, The CelCycle: An introduction, W. H. Freeman and Company)

ntrolling the cell cycle. Earlier researchers ha frog eggs (Xenopus) contained all the necess ired for DNA replication. This included protei noting factor (MPF). At the time of this study, ity and the research group wanted to test usi 1. In Figure 1 (a) MPF activity was tested for it ne (H1 in snerm chro matin ove hromatin ortain p

ntrolling the cell cycle. Earlier researchers ha frog eggs (Xenopus) contained all the necess ired for DNA replication. This included protei noting factor (MPF). At the time of this study, ity and the research group wanted to test usi 1. In Figure 1 (a) MPF activity was tested for it ne (H1 in snerm chro matin ove hromatin ortain p

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter10: Cell Division And Mitosis

Section: Chapter Questions

Problem 1ITD: Biologists have long been interested in the effects of radiation on cells. In one experiment,...

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Biologists have long been interested in the effects of radiation on cells. In one experiment, researchers examined the effect of radium on mitosis of chick embryo cells growing in culture. A population of experimental cells was examined under the microscope for the number of cells in telophase (as a measure of mitosis occurring) before, during, and after exposure to radium. The results are shown in the Figure. What is the effect of radium exposure on mitosis? Source: R. G. Canti and M. Donaldson. 1926. The effect of radium on mitosis in vitro. Proceedings of the Royal Society of London, Series B, Containing Papers of a Biological Character 100:413419.
"Agent V" is the name of an anticancer (chemotherapy) drug. This drug works against cancer cells by inhibiting the formation of microtubules in sensitive cells. Consider a cell that is sensitive to agent V (in other words, agent V is effective at stopping growth of this cell). Based on this information, agent V would cause the cell to be frozen at which of the major cell cycle checkpoints (G1, G2 or M checkpoint)? Explain
Maturation promoting factor, MPF, is a cyclin-CDK complex that catalyzes the phosphorylation of other proteins to start mitosis. The activity level of MPF is dependent on the relative concentrations of the cyclin and CDK components of MPF (Figure 1). Based on Figure 1, which of the following describes the role of cyclin in the regulation of the cell cycle? a.During S phase, the cyclin level remains the same because DNA replication is occurring. b.During G2 phase, the cyclin level remains low, causing MPF activity to decrease, which leads cells to initiate mitosis. c.During G1 phase, the cyclin level decreases to signal the start of the resting phase of the cell cycle. d.During M phase, the cyclin level peaks, resulting in an increased binding frequency with CDK.
Progression through the cell cycle is dependent on both extra- and intracellular conditions. Consider the following conditions. Indicate which checkpoint (s) responds to that condition.a. The cell is large enough to divide.b. The DNA is completely copied during S phase.c. The cell is receiving positive cues from neighbors.d. The DNA is damaged.e. The cell has enough energy reserves to divide.f. Are all the sister chromatids correctly attached to spindle microtubules?
Amount of DNA per nucleus over the cell division cycle. At which point in the accompanying figure does MPF reach its highest activity during the cell division cycle? a) I b) II c) III d) IV
Passage of cells from G1 through R to S depends on the interaction of various signal molecules, proteins and enzymes which regulate the cell cycle. Imagine I have just induced a mutation in a cell line which prevents the breakdown of the cyclin molecule we discussed. Which of the following events do you predict will happen? circle all that apply Select one or more: a. Uncontrolled cell replication may result b. Retinoblastoma protein will be continuously active c. The cells will be stuck in G1 phase d. The cells will begin to replicate their DNA e. Cyclin dependent kinase (Cdk) will be continuously active
Q. Cyclins and CDK(inase) complexes regulate the cell cycle. Which of the following statements is true? A. Cyclins activate CDKs which remove phosphates from other proteins. B. Cyclins activate CDKs which add phosphates to other proteins. C. CDKs activate cyclins which remove phosphates from other proteins. D. CDKs activate cyclins which add phosphates to other proteins.
In the experiment below, you have treated cells with different cancer drugs, stained them with propidium iodide, and analyzed them by flow cytometry. Which of the following histograms illustrates what you would expect to see in the event that the spindle assembly checkpoint is activated (focus on the solid line, the dotted line is normal cell cycle control)? 1. D 2. C 3. A 4.B
Explain Cyclin-dependent kinases (CDKs) control the cell cycle by phosphorylating other proteins?
Explain why we can say that M-phase of the cell-cycle is triggered by a positive feedback loop. a) What would the consequences be if cohesins were working normally but condensins were not? and b) what stage of the cell cycle would this cause problems in? Why is it important for the centrosome to duplicate during G1-G2 (interphase) before M phase? The kinetochores serve as a link between the sister chromatids and the microtubules attached to the mitotic spindle. a) How are microtubules still able to exhibit dynamic instability after they are bound to the sister chromatids and b) why is this important to mitosis? As the name suggests, the Anaphase-promoting-complex (APC), promotes the 4th phase of mitosis by separating the sister chromatids so they can travel to separate poles of the cell, and prevents them from being re-zipped together. Describe how APC does these two things (Hint: one involves M-cyclin and the other involves…
One approach to studying the regulation of cell cycle progression (particularly in an era when genetic and molecular biology manipulations were less readily accomplished in mammalian cells) was to use treatments that induced cells to fuse and then monitor the behavior of the two nuclei in the resulting cell. The figure below depicts data from one such study. The investigators did preliminary work to produce populations of cells that were synchronized in various stages of the cell cycle (G1, S, or G2 in the examples shown below). They then fused the cells in different combinations and monitored subsequent events in each of the nuclei. For purposes of this question, we will pay particular attention to what occurred in the nucleus that came from the cell in G1. In one experiment (I), cells in the G1 and S phases were fused. That event caused the nucleus from the G1 cell to very quickly enter the S phase (sooner than it would otherwise have done so). In contrast, in a second experiment…
One approach to studying the regulation of cell cycle progression (particularly in an era when genetic and molecular biology manipulations were less readily accomplished in mammalian cells) was to use treatments that induced cells to fuse and then monitor the behavior of the two nuclei in the resulting cell. The figure below depicts data from one such study. The investigators did preliminary work to produce populations of cells that were synchronized in various stages of the cell cycle (G1, S, or G2 in the examples shown below). They then fused the cells in different combinations and monitored subsequent events in each of the nuclei. For purposes of this question, we will pay particular attention to what occurred in the nucleus that came from the cell in G1. In one experiment (I), cells in the G1 and S phases were fused. That event caused the nucleus from the G1 cell to very quickly enter the S phase (sooner than it would otherwise have done so). In contrast, in a second experiment…