Question

2) In class we looked at one modern method for examining microtubule dynamics in vivo, which is to use Microtubule end binding proteins like EBI, a protein that binds to the GTP-bound tubulin filaments. a. [4pts) Based on the model of Dynamic Instability, if you watched the mitrotubules in a cell in GO over time using a red fluorescent version of tubulin, and a green fluorescent version of EBI what would you expect to see? b. (4pts) If this particular cell had a lot of microtubule treadmilling rather then just dynamic instability how would your answer above change? c. (4pts) Regardless of the dynamics of your microtubules, if you added a drug that inhibited the activity of kinesin, the plus-end directed microtubule motor protein, what types of effects might you expect to see in a secretory cell in GO?

I just want to see if the answers are right, so for 1a. since the microtubule is in a cell that's in G0, would there be no movement since everything stops in G0 phase? Or are the microtubules continously depolymerizing/polymerizing at a constant rate?

For 1b. I said the same thing since the cell is in G0 phase then it wouldn't matter if it was microtubule treadmilling, it wouldn't be moving.

1c. I'm not sure what exactly would happen

I'm just a bit confused about what happens during G0 phase, does everything stop being active in G0 phase? Or are they active just at a controlled rate??

Answer 1

1)

• The microtubules doesnot divide in this state .
• When the cell receive signal to divide it starts dividing and enters the next phase.
• Normally Microtubule assembly is produced which divide in the initial stages of prophase.

2)

• Here they say that in G0 phase if there is microtubule division then you can see expression as it is bound to GFP .
• They say that there is presence of treadmilling in above case . So you will see expression or moving of cells.

3)

• If the drugs that stop Kinesin is added before G0 phase , then the cells will not under go mitosis itself.
• It doesnot enter G0 phase which leads to cell death.