Biochemistry 2280A Study Guide - Quiz Guide: Lac Operon, Lac Repressor, Allolactose

• School: Western University
• Department: Biochemistry
• Course: Biochemistry 2280A
• Professor: Mclachlin

Document Summary

Operon: cluster -> genes -> transcribed -> same promoter producing polycistronic mrna. Transcriptional start site -> olac -> operator seq. Structural regions -> encode -> transcription -> proteins. >>lac z -> b-galactosidase ->> hydrolyses lactose -> glucose & galactose. Glucose: determines production of proteins required for hydrolysis, lactose absence -> repression of operon. Repressor -> binds -> transcription start site -> operon (operator site) > preventing rna polymerase -> removing promoter sequence (p) >>prevents -> initiation -> hydrolysis: lactose presence -> inducer -> (de-repression) Controlled -> negative feedback: possibility -> lac operon function -> determined by glucose conc, actual function of lac operon -> determined by lactose presence. Absence of glucose & presence of lactose = functional -> on. Absence of glucose & absence of lactose = non-functional -> off. Presence of glucose & presence of lactose = non-functional -> off. Presence of glucose & absence of lactose = non functional -> off.