BIOL239 Lecture Notes - Lecture 9: Lac Repressor, Lac Operon, Beta-Galactosidase
17 Apr 2016
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Polycistronic: one mrna with 2 or more transcribed genes on it. Not all genes are being transcribed at all times. There are regulatory proteins that bind to dna that can either inhibit or make transcription happen. The presence of lactose induces the expression of the genes required for lactose utilization. Addition of lactose to growth medium induces a 1000-fold increase in the production of lac permease and beta-galactosidases: monod and jacob. Inducer- allolactose: evidence for a lac repressor protein: Mutation in another gene, lacl, results in mutants that synthesize beta- galactosidase and lac permease, even in the absence of lactose. There are examples of constitutive mutants, ones who result in protein synthesis, irrespective of env. Conditions: if lactose isn"t around, its not brought into the cell, it doesn"t turn to allolactose, the repressor protein can bind to the operator and has a constitutive expression,
