Microtubule system is dramatically reorganized when an interphase cell enters mitosis. In order to investigate the mechanisms of this transition, you compare the microtubule dynamics in interphase and mitotic cells. You have cells expressing fluorescently labeled tubulin to do your assays, as well as all necessary equipment.
5.1. As a first approach, you test the dynamics of microtubule population by fluorescence recovery after photobleaching (FRAP).
(a) How do you do this experiment?
(b) Present the expected results in a graphical form plotting the rate of recovery (Y-axis) versus a stage of the cell cycle (X-axis). Include individual phases of mitosis on X-axis.
5.2. In the next experiment, you want to test more precisely how behavior of individual microtubules changes. For this purpose, you acquire time-lapse movies of living cells with fluorescently labeled microtubules and determine the following parameters of microtubule dynamics (see table below). In the right column of the table, predict a change of these parameters (e.g., increase, decrease, no change, or not sure) between the interphase and mitotic cells. (Note: “Not sure” is a valid answer for some parameters, but you are expected to enter some more definite predictions)
|
Parameter |
Change in the parameter |
|
Rate of microtubule elongation |
|
|
Rate of microtubule shrinkage |
|
|
Frequency of catastrophes |
|
|
Frequency of rescue |
|
|
Frequency of nucleation events |
|
