Lab 10: Lac operon Flashcards
What were the 3 strains of E. coli used in lab 10?
Wildtype, LacZ mutant and LacI mutant
What is the LacZ gene?
Beta-galactosidase, the functional enzyme responsible for lactose breakdown
Why did we not use lactose to induce the Lac operon?
Lactose will get broken down and only provides short-term induction
What did we use to induce the Lac operon?
TMG. An analog of lactose that doesn’t get broken down
How does TMG induce the Lac operon?
It binds to the repressor and inactivates it so transcription can occur
How do we measure the activity of beta-galactosidase?
By using X-gal instead of lactose. When cleaved by beta-galactosidase it produces a blue product. Activity is measured based on how blue the solution is
What is the LacI gene?
The gene that encodes the repressor for the Lac operon
What were the colours for the uninduced and induced wildtype strain cells?
No colour for the induced samples, light blue for the induced sample
What were the colours for the uninduced and induced LacZ mutant strain cells?
No colour for uninduced and induced
Why was no colour seen for either sample of the LacZ mutant cells?
This strain has a mutation that knocks out the function of beta-galactosidase. X gal can’t be cleaved to produce the blue product regardless if the operon is induced or not
What were the colours for the uninduced and induced LacI mutant strain cells?
Dark blue for both uninduced and induced
Why were both samples of the LacI mutant cells dark blue?
This strain has no repressor. Transcription can never be turned off so it doesn’t matter if it was induced or not
