Chapter 12: The Cell Cycle – Flashcards

Unlock all answers in this set

Unlock answers
question
What is the correct order for the phases of the cell cycle?
answer
S,G2,M,G1
question
Although the process of chromosome partitioning during mitosis is visible through a light microscope, the process of DNA replication is not. Why?
answer
Chromosomes are too extended during S phase to be seen by light microscopy.
question
A certain species of animal has six pairs of chromosomes. How many sister chromatids do the nuclei of these animals have during G2 phase?
answer
24
question
The length of the different phases of the cell cycle can be measured by performing a pulse-chase experiment with radioactive thymidine and waiting to see how long it takes for radioactivity to appear in mitotic chromosomes. After the radioactivity first arrives in mitotic chromosomes, it is observed that the amount of radioactivity in these chromosomes increases steadily over several hours, reaches a plateau, and then declines. What cell-cycle phase is measured by the time between the first and last appearance of radioactive thymidine in condensed, mitotic chromosomes?
answer
S phase
question
The length of the different phases of the cell cycle can be measured by performing a pulse-chase experiment with radioactive thymidine and waiting to see how long it takes for radioactivity to appear in mitotic chromosomes. What cell-cycle phase is measured as the time between the end of radioactive thymidine labeling and the beginning of the appearance of radioactive mitotic chromosomes?
answer
G2 phase
question
Mitotic spindle fibers are composed of what cellular components?
answer
Microtubules
question
During mitosis, it is necessary for the nuclear envelope of the parent cell to disintegrate. This is accomplished in part by phosphorylation of proteins associated with the nuclear envelope. If the enzyme responsible for that phosphorylation event is inhibited, at which phase of mitosis are cells likely to arrest?
answer
Prometaphase
question
Taxol is a drug that stabilizes microtubules and prevents them from depolymerizing. Consequently, cells treated with taxol fail to complete mitosis. What is the last stage of mitosis that taxol-treated cells are likely to complete?
answer
Metaphase
question
What would be the effect on the cell cycle of interphase frog oocytes if chromosomes from M phase oocytes were injected into them?
answer
Nothing would happen
question
One interesting experiment conducted with frog oocytes revealed that with an appropriate stimulus, the cyclic appearance and disappearance of cyclin occurs even in the absence of a nucleus. What does this result imply about the production of cyclin in oocytes during the cell cycle?
answer
Cyclin is synthesized using preexisting mRNA.
question
Much of what is known about the function of cyclin and Cdk was learned by mutations in yeast. One yeast mutant is known as wee1. As its name implies, this yeast mutant never achieves full size. It divides continuously without allowing time for the cells to grow to their normal size. The defect is caused by inactivation of a gene that encodes a protein kinase. What might be a possible role for this kinase in normal wild-type yeast?
answer
It may phosphorylate and inhibit the activity of mitotic Cdk.
question
In an experiment to determine whether M-phase cells contain a regulatory molecule that initiates mitosis, cytoplasm from M-phase cells and interphase cells was injected separately into interphase cells. Why did researchers inject cytoplasm from interphase cells?
answer
As a negative control, to show that the injection itself doesn't have an effect on the cell cycle
question
Which of the following conditions will most likely prevent a cell from passing the G1 checkpoint?
answer
DNA is damaged.
question
What mistake during anaphase can contribute to cancer formation?
answer
Improper separation of sister chromatids
question
Early detection is the key to successful treatment of most cancers. Why?
answer
If caught early enough, cells from the primary tumor are less likely to have traveled to new sites and started secondary tumors.
question
Many cancers are due to the failure of cells to properly regulate the _____ checkpoint during the cell cycle.
answer
G1
question
Exposure to chemicals that cause mutations in DNA greatly increases the chance of developing cancer. Mutations that inactivate which of the following proteins would most likely lead to cancer?
answer
Rb (retinoblastoma) protein
question
The consequence of E2F inactivation is that _____.
answer
cells are unable to enter S phase
question
Progression though the cell cycle is regulated by oscillations in the concentration of which type of molecule?
answer
Cyclins
question
After the S phase, what compromises a single chromosome?
answer
Two sister chromatids
question
What evidence suggest that during anaphase, kinetochore microtubules shorten at the kinetochore?
answer
Daughter chromosomes were observed to move toward the pole faster than do the marked regions of fluorescently labeled kinetochore microtubules
question
Under normal conditions, what happens to the cell cycle if the chromosomes fail to separate properly at anaphase?
answer
The cycle would arrest in M phase, and cytokinesis would never occur.
question
Chromatin is ____
answer
A DNA-protein complex that makes up chromosomes
question
Which processes rely on a constricting ring of fibers?
answer
Cleavage furrow formation in animals and bacterial fission
question
Active MPK-CdK phosphorylates proteins that cause what?
answer
M-phase initiation
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New