Bio Q !!!!

[lintydent]

.....This is from topscore:

Which of the following best describes gene regulation and expressoin in a repressible system?

A. The respressor binds to the operator, forming a barrier that prevents genes from being transcribed.
B. The repressor is inactive until it combines with the corepressor allowing genes to be transcribed.
C. The repressor-corepressor binds to the operator and represses enzyme synthesis.
D. In a constant state of transcipription without a corepressor.
E. C&D


What's the answer? I'm not sure if I agree with topscore....they say E. I say A. Am i going crazy? Or stupid?

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[ConfusedOne]

I believe 'a' describes an inducible system (eg lac operon) while 'e' describes a repressible system. In a repressible system, the repressor must be activated by a corepressor

 

[dat_student]

.....This is from topscore:

Which of the following best describes gene regulation and expressoin in a repressible system?

A. The respressor binds to the operator, forming a barrier that prevents genes from being transcribed.
B. The repressor is inactive until it combines with the corepressor allowing genes to be transcribed.
C. The repressor-corepressor binds to the operator and represses enzyme synthesis.
D. In a constant state of transcipription without a corepressor.
E. C&D


What's the answer? I'm not sure if I agree with topscore....they say E. I say A. Am i going crazy? Or stupid?

With repressible systems, the binding of the effector molecule to the repressor greatly increases the affinity of repressor for the operator and the repressor binds and stops transcription. I'd pick E

 

[electron]

There are two different systems when it comes to Gene Regulation

Inducible System (eg. lac operon) - which has an active repressor which stops the expression of genes unless an inducer is available.

Repressible System - has an inactive repressor allowing gene expression unless a corepressor is available.

You were thinking of an inducible system

 

[lintydent]

alright....just gave myself a big whack in the forehead.

anyone care to do seconds....