Question

You are given a flask with liquid media containing a population of S. pombe cells that 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 S-cyclin. Which FACS plot (see attached figure) best represents how cells in this flask would appear following growth for 2 hours at the restrictive 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.com, #2 #3 #4 #5 #6 *4 i į i relative amount of DNA percell ż i 2 1 2 #2 #3 ooooo #4 #5 #6

Answer 1

Cyclin S are important for DNA replication and will be present till late G2 phase and if the cyclin S is mutated in restricted temperature , the cell cannot proceed after G1 phase and cells will accumulate in G1 phase itself

Hence the answer is #3

It has only cells in G1 phase