Biology 1002B Lecture Notes - Lecture 13: Reading Frame, Silent Mutation, Indel
Document Summary
Operator short binding regulatory dna sequence in operon to turn on/off gene. Repressors/activators control 1 operon: repressor reduces transcription, activator increases transcription, e. coli metabolism of lactose: inducible lac operon. No lactose (normal: lac repressor electrostatically (+ and charges on double helix; not base pairing) bind to operator. Often proteins that bind to dna bind as a dimer and stabilizes looped out dna. Block rna polymerase from binding to promoter and transcribing. When lactose is present, lac operon is turned on: lactose + low levels of -galactosidase allolactose (isomer of lactose, allolactose is an inducer (help increase expression) for lac operon. Binds to lac repressor and alter its conformation so it can no longer bind to operator. Rna polymerase can then bind to promoter upstream of laz z and start transcription. Not translated since there is no sd box, start and stop codon. Amino > trp > carboxyl: likely effect of base sequence substitutions in various dna signals.