Lac Operon?

Question

By a single regulatory protein the 'Lac operon' undergoes-?

1. positive regulation
2. Negative regulation
3. Both
4. None

Please answer me..

! more question.
Its the previous one but replace Lac Operon to Arabinose Operon.
Please help me.

Answer 1

This is an example of negative regulation. The mechanism is that Lactose binds to the repressor protein which releases from the DNA promoter thereby allowing transcription of mRNA and subsequent production of the protein that degrades lactose. Thus, the gene is "turned off" until the desired substrate appears, which is a nice example of conservation of energy, since the bacteria doesn't make the protein unless the substrate is there to be utilized.

In contrast, positive regulation would be where something binds to a protein which then binds to the DNA promoter and "turns on" a gene.

Arabinose operon is different, it works by both negative and positive regulation, for details, see:

http://www.pnas.org/cgi/content/abstract/77/6/3346
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mga.section.2165

Answer 2

that's between the least difficult bacterial gene regulation structures there is, yet as quickly as you be attentive to the way it works, it is fairly extremely exciting. think of of it like this. The cellular can use lactose as a carbon source, yet does not have the want to make the enzymes it desires to make to try this except lactose is contemporary otherwise which would be a waste of capability and aspects. So... there's a repressor protein that sits on the DNA and stops transcription. whilst the sugar lactose is contemporary. It (lactose) gets into the cellular and binds to the repressor protein. This reasons the protein to drop off of the DNA and transcription (and translation) of the enzymes mandatory for the metabolism of lactose proceeds. Glucose is yet another and extra powerful carbon source than lactose. micro organism can get extra capability from glucose than they might from lactose, yet whilst there is not any glucose contemporary, a micro organism that would in basic terms make the main of glucose could starve. enter the lac operon and the thank you to furnish micro organism with the equipment to hire lactose as a secondary foodstuff source.

Answer 3

It depends on what cellular process you are talking about. We need more information.