01:119:115 Lecture Notes - Lecture 16: Lac Operon, Allolactose, Operon
Document Summary
Topic 16 - gene regulation: prokaryotic gene regulation. Only a certain subset of genes are used at any given time. Always needed + constantly transcribed (genes in respiration) Other genes are only transcribed when needed: lac operon model. 3 genes for lactose metabolism in e. coli on dna. If no lactose - cell does not make these enzymes. If lactose is present - enzymes are made. Operon = a group of genes controlled by a single regulatory signal -> controlled by an operator. You control whether or not you"re making the mrna copy using this operator. Either all enzymes or non at all. Operans are : sequence of dna that includes: Operator : short stretch of dna -> switch . Promoter and operator are binding sites on dna - not transcribed. Usually off transcription needs to be turned on. To turn on- an inducer molecule inactivates the repressor. Repressor prevents transcription (repressor is a constitutive gene)