You are given a flask with liquid media containing a population of S. pombe cell
ID: 210417 • Letter: Y
Question
You are given a flask with liquid media containing a population of S. pombe cells have a temperature sensitive mutation of a gene that causes complete loss of function of the gene product at the restrictive temperature. The flask had been incubating at the permissive temperature before it was given to you, and the cells in the flask were replicating asynchronously with respect to the stage of the cell cycle.
The mutated gene in this strain of yeast encodes an essential subunit of a DNA polymerase required for DNA replication, but not DNA repair. (Assume that the cell only has one DNA polymerase that performs DNA replication and that cells paused in DNA replication can restart and complete this process).
Which FACS plot (see attached figure) best represents how cells in this flask would appear following growth after 2 hours in culture at the restrictive temperature followed by 60 min in culture at the permissive temperature ?
(Note, assume that FACS plot #1 shows analysis of a population of S. pombe replicating asynchronously (i.e. each cell within a population is at a random stage of the cell cycle) in culture. In the rich media assume the yeast have a cell cycle time of 100 min, with G1=50 min; S = 25 min; G2 = 15 min and M = 10 min).
#1 #2 #3 #4 #5 #6 cells in G phase cells in Gjand M phases cells in S phase 2 relative ameunt of DNA per cell (arbitrary units) #2 #4 #5 O #6 O #3Explanation / Answer
my opinion Flac plot four is correct answer. this is because the temperature has been controlled thus, the mutation will work actively. since it is a DNA damage checkpoint so at the phase of damage there will be complete loss of activity. and then the function will resume. This kind of activity can be easily seen in plot 4 only in comparison with other plots.
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