Part A - Short Answer
If tryptophan (trp) codons containing two trpcodons in its leader region were mutated to serine (ser)codons, then a high level of expression of the mutated operon wouldbe visible ONLY if trp and ser were absent at the sametime from the media. Explain why this occurs.
Part B - Multiple Choice
Circle the correctrelationship between the trp operon and the repressor.
- The repressor acts in 'cis'.
- The repressor protein is responsible for the formation of the\"termination\" stem loop.
- Binding of the repressor protein leads to attenuation of thetrp operon.
- Ă‚Â Ă‚Â The presence of tryptophan results in increasedexpression of the tryptophan gene
- When bound to tryptophan, the repressor is able to bind theoperator of the trp operon
Part C - Multiple Choice
Before transcription of the lac operon can commence, RNApolymerase must strongly bind to the promoter.Circle the correct statement asto why this occurs.
- lacI+ is mutated to lacI-
- a CAP-cAMP complex binds to the CAP site in the promoter in theabsence of glucose.
- CAP binds to the CAP site in the promoter in the presence ofglucose.
- catabolite repression occurs in the presence of glucose.
- catabolite repression occurs in the absence ofglucose.
