Question

Which of the following statements about gene regulation concerning operons is INCORRECT? A) A negative repressible gene is controlled by a regulatory protein that inhibits transcription. B) For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA. C) For a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator. D) A regulator gene has its own promoter and is transcribed into an independent mRNA. E) Presence of operons where genes of related functions are clustered is common in bacteria but not in eukaryotes.

Answer 1

Answer:

B) For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA.

Explanation:

Operon is usually present in prokaryotes. It has a group of genes being transcribed under the same promoter. So the genes are expressed together when required. An operon can be under negative or positive control. It can further be inducible or repressible.

Under negative repressible control the operon is normally in working condition. Repressor protein is present but unable to bind to the operator. When a corepressor binds to repressor, it is activated and finally binds to the operator halting the transcription process. Hence the small molecule (corepressor) leads to binding of repressor to DNA and not the other way round.  A small molecule is required to prevent the gene's repressor from binding to DNA in case of negative inducible operon.

Answer 2

Answer:

The answer is B

Explanation:

For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA