Which of the following statements about the positive control

Which of the following statements about the positive control of gene expression are true? Check all that apply. The regulatory molecule needs to be provided to the DNA for transcription to occur. The regulatory molecule needs to be removed from the DNA for transcription to occur The regulatory molecule stimulates transcription. The regulatory molecule interferes with transcription. Submit My Answers Give Up Part B Which of the following statements about the negative control of gene expression are true? Check all that apply. The regulatory molecule needs to be removed from the DNA for transcription to occur Binding of the regulatory molecule to DNA stimulates transcription The regulatory molecule interferes with transcription The regulatory molecule needs to be provided to the DNA for transcription to occur

Solution

positive control of gene expression- A and C

In positive regulation, a transcription factor is required to bind at the promoter in order to enable RNA polymerase to initiate transcription.

negative control of gene expression- A and C

In negative regulation a repressor protein binds to an operator to prevent a gene from being expressed. therefore, it has to be removed.

inducible system- C and D

for example, in lac operon, the repressor binds to operator inhibiting its transcription. when lactose is present, it binds to repressor inactivating it and thus enabling RNA polymerase to bind to operator and continue transcription..

repressible system- A and D

in tryptophan operon, the repressor is normally inactive. but when tryptophan is present, it acts as corepressor and binds to repressor and binds to operator to inhibit transcription.