1. A student attempted to determine the length of each phase of the cell cycle i
ID: 9299 • Letter: 1
Question
1. A student attempted to determine the length of each phase of the cell cycle in a civet cell line. The student counted the number of cells in a culture and found that the number doubled every 23 hr. BrdU, a DNA precursor that can be detected by immunofluorescence microscopy, was added to the culture medium for 15 minutes and, then, the cells were transferred to BrdU-free culture medium. Cells were fixed immediately after removing the BrdU and at 0.5 hour intervals. The samples were processed for immunofluorescence using anti-BrdU antibodies. The results were:i) 43 out of 164 cells fixed immediately after removal BrdU were stained by anti-BrdU.
ii) 8.0 hr after labeling, 0 of 12 mitotic* cells stained with anti-BrdU; at 8.5 hr, 0 of 16 mitotic cells were stained; at 9.0 hr 2 of 16 mitotic cells were stained; at 9.5 hr 16 of 16 mitotic cells were stained.
(mitotic cells are all cells in prophase, prometaphase, metaphase and anaphase)
iii) The first BrdU positive cells in late telophase were seen at 10.5 hr after labeling.
2A. Determine the length of G1, S, G2 and mitosis. How these were determined should be clear from your answer. (4 points, show your calculations)
2B. How would you determine the percentage of cells that were in G0? (1 point )
Explanation / Answer
The length of G2 is equal to the amount of hours that has passed after the first couple of mitotic cells were seen to be stained.
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