Discussion
Which of these best describes an operon?
Answer: B
Correct answer: A cluster of genes transcribed together from a single promoter
An operon is a group of adjacent genes transcribed together as one messenger RNA from a single promoter, so that functionally related proteins are produced in coordinated amounts. The arrangement is characteristic of prokaryotes and was described by Jacob and Monod in 1961. Its parts are the promoter, where RNA polymerase binds; the operator, where a regulatory protein binds; and the structural genes. A separate regulator gene encodes the protein that binds the operator. The lac operon is inducible: a repressor blocks transcription until lactose - through its isomer allolactose - binds the repressor and removes it, so the genes are expressed only when their substrate is present. The trp operon is repressible: it is transcribed until tryptophan accumulates and activates the repressor, switching it off. The two illustrate the general principle that catabolic pathways are induced by their substrate and anabolic ones repressed by their product.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development