Chapter 18 Practice Quiz Questions
Which one of the following statements about apoptosis is true?
Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.
You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6?
Cells will be unable to complete DNA synthesis.
MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment?
Components of an interphase nucleus are insufficient to cause mitotic spindle formation.
Which organelle fragments during mitosis?
Golgi apparatus
Which one of the following statements is true?
In anaphase B, microtubules associated with the cell cortex shorten.
Which of the following statements about the anaphase-promoting complex (APC) is false?
It is continuously active throughout the cell cycle.
Which of the following statements about kinetochores is true?
Kinetochores assemble onto chromosomes during late prophase.
Which one of the following statements regarding mitosis is true?
Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.
Which of the following statements is false?
The activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active.
Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2?
The cell would enter M phase under conditions when normal cells would not.
What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?
The cells produced would get smaller and smaller
Which one of the following statements is false?
The cleavage furrow always forms in the middle of the cell.
Which of the following statements is false?
The loading of the origin recognition complexes (ORCs) is triggered by S-Cdk.
Which of the following statements is true?
The mitotic spindle helps segregate the chromosomes to the two daughter cells.
Which of the following events does not usually occur during interphase?
The nuclear envelope breaks down.
Is the following statement true or false?After the nuclear envelope breaks down, microtubules gain access to the chromosomes and, every so often, a randomly probing microtubule captures a chromosome and ultimately connects to the kinetochore to become a kinetochore microtubule of the spindle.
True
Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution?
Yeast cells have only one Cdk, whereas humans have many Cdks.
Of the following mutations, which are likely to cause cell-cycle arrest?
a mutation that removed the phosphorylation sites on the Rb protein
When introduced into mitotic cells, which of the following is expected to impair anaphase B but not anaphase A?
an antibody against the motor proteins that move from the minus end of microtubules toward the plus end
Condensins ________________.
assemble into complexes on the DNA when phosphorylated by M-Cdk
Which of the following precede the re-formation of the nuclear envelope during M phase in animal cells?
assembly of the contractile ring
Programmed cell death occurs ________________.
by means of an intracellular suicide program
Apoptosis differs from necrosis in that necrosis ________________
causes cells to swell and burst, whereas apoptotic cells shrink and condense
The principal microtubule organizing center in animal cells is the ____________.
centrosome
At the end of DNA replication, the sister chromatids are held together by the ___________.
cohesins
Levels of Cdk activity change during the cell cycle, in part, because ________________.
cyclin levels change during the cycle
A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to ________________.
disassemble its nuclear lamina at prometaphase
Cells in the G0 state ________________
do not divide
Which of the following does not occur during M phase in animal cells?
growth of the cell
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 following graphs are obtained. Which of the following would not explain the results with the mutant?
inability to begin M phase
You have isolated a strain of mutant yeast cells that divides normally at 30°C but cannot enter M phase at 37°C. You have isolated its mitotic cyclin and mitotic Cdk and find that both proteins are produced and can form a normal M-Cdk complex at both temperatures. Which of the following temperature-sensitive mutations could not be responsible for the behavior of this strain of yeast?
inactivation of an enzyme that ubiquitylates M cyclin
The G1 DNA damage checkpoint ________________.
involves the inhibition of cyclin-Cdk complexes by p21
Disassembly of the nuclear envelope ________________.
must occur for kinetochore microtubules to form in animal cells
Cytokinesis in animal cells ________________.
requires ATP
Which of the following statements is false?
Motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall.
Which of the following statements about the cell cycle is false?
Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eucaryotic cells.