Conditional mutants

[Penny]

Hi all,

 

In one of my biochemistry courses, we went over the cdc (cell division cycle) mutant screen using conditional mutants (temperature sensitive). Yeast cells were exposed to ultraviolet light (to cause DNA mutations). Next, they were plated and incubated at 25 degrees, then replica plated and incubated at 37 degrees. The temperature sensitive clones were isolated and examined for cdc mutants.

 

I am a little confused about the conditional mutants in general so my questions are...

 

1. What is the purpose of incorporating conditional mutants in an experiment? (I guess my question really is, how do they know the temperature sensitive clones contain cdc mutants?)

2. How exactly is it done? (If the explanation is really long and you don't want to do it, you can point me in the direction of some papers =D.)

 

Thank you so much!

 

Penny

[CharonY]

Hint:1: were the cells wild-type or mutants before you exposed them to UV?

Hint 2: cdc mutants are generally temperature sensitive.

[Penny]

Hint:1: were the cells wild-type or mutants before you exposed them to UV?

Hint 2: cdc mutants are generally temperature sensitive.

 

If the yeast cells were cdc mutants before the UV irradation, then they won't be able to grow. Their cell division cycles would be disrupted. The cells would have to be wild-type before UV exposure.

 

So................ would there be a "temperature" gene near the cdc gene? Upon UV exposure, both genes are mutated, causing the mutant cells to be also temperature-sensitive?

 

LOL Pure guess. I hope I didn't go too far off the tangent.

 

Thanks for your response, CharonY!

 

Penny

Edited September 15, 2010 by Penny

[CharonY]

You have not integrated the second hint. Or think about this: are cdc mutant completely unable to grow? Regardless of the condition? Moved to homework.

Edited September 15, 2010 by CharonY

[dttom]

I am not sure, but is it about if a mutant clone is temperature-sensitive, say growth inhibited at 37c, it could still grow quite well at 25c, so when you meet a clone that is nearly absent at one temp but present at another, it implies there might be some mutation in cdc?