repressible system

[JohnDoeDDS]

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Im not getting it why the answer I got is wrong. Here is the question:

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

A) The repressor 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 transcription without a corepressor.
E) C&D

I got A for this. And it is wrong. Could someone explain this please?

 

[yorkiepoo]

I would have said A too....


????

 

[Fariba]

Im not getting it why the answer I got is wrong. Here is the question:

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

A) The repressor 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 transcription without a corepressor.
E) C&D

I got A for this. And it is wrong. Could someone explain this please?

The answer is E - because in a repressible system, remember that the repressor, by itself, is not in its active state - it needs to bind to the corepressor... otherwise its just kinda hanging around. Once, it binds the corepressor, then together they can bind to the operator and repress synthesis. Kaplan explains this really well, too.

 

[egots]

the answer is E...in the represser system u need to have the represser and the corepressor attached to the operon to prevent transription otherwise it will be in a constant state of transcription...make sure you read the question right b/c you are think of hte inducer system

 

[tinman831]

Is the answer C? I think you need an effector molecule (corepressor) to bind to the repressor, which increases the repressors affinity to the operator.

 

[yorkiepoo]

i am pretty sure it is A... because no other options refer to a repressible system.. what is the answer in the book?

 

[jkh1886]

Im not getting it why the answer I got is wrong. Here is the question:

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

A) The repressor [binded to a corepressor] 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 [Inhibited].
C) The repressor-corepressor binds to the operator and represses enzyme synthesis.
D) In a constant state of transcription without a corepressor.
E) C&D

I got A for this. And it is wrong. Could someone explain this please?

1

 

[JohnDoeDDS]

Topscore question.

Answer is E.

 

[tinman831]

Topscore question.

Answer is E.

Oops I didn't realize there was a C and D. Well... in addition to what I wrote earlier, if you don't have the effector molecule (corepressor) then the repressor can't bind to the operator and the genes are constantly transcribed.

 

[JohnDoeDDS]

the answer is E...in the represser system u need to have the represser and the corepressor attached to the operon to prevent transription otherwise it will be in a constant state of transcription...make sure you read the question right b/c you are think of hte inducer system

Wo you are right! I think I am thinking of the inducer system and now I am confused.

Could someone explain the difference between the represser system and the inducer?

 

[tinman831]

Wo you are right! I think I am thinking of the inducer system and now I am confused.

Could someone explain the difference between the represser system and the inducer?

In a repressible system the effector molecule (the corepressor) binds to the repressor allowing this complex to bind to the operator and block transcription. In an inducible system, the effector molecule binds to the repressor and inhibits the repressor.

 

[TeethRCool]

Wo you are right! I think I am thinking of the inducer system and now I am confused.

Could someone explain the difference between the represser system and the inducer?

Inducible system means that it is usually off---> genes arent transcribed-------->repressor is always on the operator. However.. with an inducer the inducer will form a complex with the repressor so that this inducer-repressor complex cant bind to the operator---> genes can be transcribed.

Repressible system means that it is usually on (constitutive means same thing)---> genes are always transcribed because the repressor can't bind to the operator. However with a corepressor, the repressor and corepressor form a complex which can bind to the operator---> genes aren't transcribed.

Remember, if repressor can bind to operator, NO TRANSCRIPTION.
if repressor can't bind to operator, TRANSCRIPTION!

Hope that helps.

 

[joonkimdds]

12

 

[Clover]

example of inducible - lac operon, needs lactose present to activate

example of repressible - trp operon, always making trp until too much present. trp (corepressor) stops the system from making further trp.

hope this simple explanation is helpful.

 

[JohnDoeDDS]

you guys are the best. Thanks.