Biology 172 Ch 11 – Flashcards

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question
Which of the following 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 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
One of the causes of cancer is the mutation of genes that encode proteins in the biochemical pathway regulated by PDGF. How could such mutations cause cancer?
answer
Cancer could result if the mutations caused the biochemical pathway to become permanently active.
question
The consequence of E2F inactivation is that _____.
answer
cells would be unable to enter the S phase
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