BIOL 1105 Lecture Notes - Lecture 14: Lac Operon, Trp Operon, Lac Repressor
Document Summary
Gene expression changes over time: prokaryotes regulate gene expression in response to environmental changes, eukaryotes regulate gene expression for development and to maintain homeostasis. Gene expression is controlled by: transcriptional regulation, post-transcriptional regulation, post-translational regulation. Dna binding proteins control transcription initiation: a promoter region consists of regulatory dna sequence upstream from transcription start site, rna polymerase binds to the core promoter to initiate transcription. Regulatory proteins may affect the ability of rna polymerase to bind to the promoter: eukaryotes: each gene has its own promoter sequence, prokaryotes: multiple genes controlled by one promoter. Lac transcription only occurs when lactose is present, and glucose is absent. Tryptophan produced by trp operon encoded proteins: the trp repressor inhibits transcription when tryptophan is available. Induction molecule in the environment stimulates transcription: repression molecule in the environment inhibits transcription, positive control transcription regulated by activator protein, negative control transcription regulated by repressor protein.