The following Figure 1 represent FACS analysis of cells. The dotted lines repres
ID: 86082 • Letter: T
Question
The following Figure 1 represent FACS analysis of cells. The dotted lines represent the cells progressing normally through the cell cycle. The solid lines represent cells that had been treated with a particular reagent, that affects their progression though the cell cycle. a) With reference to the cell cycle (and the dotted lines in the graphs above, which steps of the cell cycle do peaks 1 and 2 represent (and the part in between). b) Which of the following examples would best represent chronic myeloid leukemia cancer cells that had been treated with Gleevec, which causes cell cycle arrest during G1 phase. c) When G0 arrested cells are treated with a mitogen, which CDk (s) is (are) activated and which check point do the cells need to pass. d) With reference to the Rb protein, what is the function of the CDKs identified in part 4? e) C - myc is expressed as a consequence of mitogen activation but yet if c - myc is over-expressed in normal cells it does not cause cancer- (i) Refer to Figure 2 above to explain what happens in normal cells? (ii) If the ARF protein was inactivated would this cause higher rates of tumors to occur or lower rates?Explanation / Answer
a) Peak 1 and 2 represent G1 and G2 phases, and part in between shows S phase.
b) Figure 1C and 1D best represent cell cycle arrest during G1 phase because the number of cells entering S and S/G2 phase has reduced greatly in 1C and slowly reached to zero in 1D.
c) CDK-4 and CDK-6 are activated as they are growth promoters in G1 phase that is Mitogen dependent.
Checkpoints are related to DNA damage and mitosis advancement. When the cell is G0 arrested means it suffers DNA damage in G0 phase, which is propagated to G1 and to mitosis. So here checkpoint is G0.