BIOLOGY 1A03 Lecture Notes - Lecture 5: Maltose, Trp Operon, Catabolite Repression

• School: McMaster University
• Department: Biology
• Course: BIOLOGY 1A03
• Professor: Xudong Zhu

Document Summary

The lac genes are in close physical proximity! Suggested that lacz and lacy are both controlled by laci. Section of e. coli chromosome! lacl product! lacl! Galactoside permease! lacz product! lacy product! lacz! lacy! Mechanisms of negative control: discovery of the repressor. 2 ways that transcription can be regulated: negative or positive control. Negative control: when regulatory protein binds to dna and shuts down transcription. Positive control [induction]: when regulatory protein binds to dna and triggers transcription. Lacz and lacy are under both negative and positive control. Laci codes for product that represses transcription of the lacz and lacy genes. Regulation fails b/c laci+ protein [normally prevents enzyme synthesis] is inactive ie laci gene produced inhibitor that exerts negative control over lacz and lacy genes. Transcription inhibitor=repressor- binds directly to dna near or on promotor for lacz and lacy genes. Lactose interacts with repressor that makes repressor release from binding site.