Everything You Wanted to Know
But Were Afraid to Ask

Written by Nurit Kleinberger-Doron

The purpose of this tutorial is to let you experience with methods frequently used for cell cycle analysis. We present here an experimental problem. You will try to solve it by performing various virtual experiments. Each experiment will be followed by several multiple choice questions.

Take your time and examine all possibilities during each step.
Enjoy yourself!


Getting  Started

Several compounds were tested in your lab as putative cell cycle inhibitors. Your job is to study the effects of substance X on cell cycle progression and to analyze its mode of action.

In your initial screening test you exposed a non synchronized culture of exponentially growing mouse fibroblasts to substance X for 24 hrs. (1.Isn't that exposure too long?) You then evaluated the number of cells in each phase of the cell cycle by DNA staining with propidium iodide followed by FACS analysis. Look at your results:

Non treated cells
Substance X treatment

2. How does substance X affect the cells?  (Choose between wrong and possible)
A. It does not alter the cell cycle.
B. It arrests cells before the restriction point.
C. It arrests cells before the G1/S transition point.
D. It arrests cells during S phase.
E. It arests cells before the G2/M transition point.
F. It arrests cells during M phase.
G. It accelerates the transition of the cells through G0 and induces arrest in G1

Click here to check your answers.

3. Is it possible that substance X arrests cells in additional points that are not observed in this experiment? (Click here for an answer).