Question

Questions The citrate (cit) operon 1. Operons are the basic unit of gene expression in prokaryotes. Explain the role of each of these operon components in prokaryotic gene expression: structural genes, promoter, repressor, and operator 2. Fully describe the E. coli cit operon as it functions in conditions without oxygen. Include promoter, repressor and operator in your description. 3. The cit operon is under negative control. What does that mean and how is this operon negatively controlled? 4. What is the result of the cit operon being negatively controlled under conditions were oxygen is present? 5. What is the relationship between the cit operon and synthesis of the CitT transporter protein? Genetic changes in the cit operon: Mutation 6. A section of the citrate operon, including the cit T gene, was duplicated in an individual in flask #9. What precisely was duplicated? What happened in terms of operon structure after this duplication? 7. Draw a sketch of both the pre- and post mutation citrate operon. 8. How did this new arrangement facilitate the transcription of the citi primary transcript under conditions without oxygen? How did this new arrangement facilitate the transcription of the cit7 primary transcript under conditions with oxygen? 9. Application question: Was the rearrangement within the citrate operon the result of a single or multiple genetic event(s)? Explain. 10. Synthesis question: Explain the advantages and disadvantages of the citrate operon mutation in E. coli living in a flask with E. coli that do not have this mutation.

Answer 1

1) Operons are a group of genes which functions for a particular product. An operon has a promoter, a repressor, an operator and other structural genes. The works of the promoter, operator and repressor are as follows---

Promoter- A gene is expressed by transcription and translation. For transcription process, an RNA polymerase must bind to the gene segment. The promoter region serves this purpose. It enables the RNA polymerase to bind with the DNA.

Repressor- Repressor region produces a protein called repressor protein which binds to a particular region to stop or inhibit transcription process. Repressor protein ensures that unnecessary transcription doesn't take place.

Operator- Operator region is the art of the DNA where the repressor protein binds to stop the RNA polymerase from transcribing.