Mcim L11 lac operon
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- Glucose and Galactose
- Galactose is inverted relative to glucose
A section of DNA that contains the genetic code for a single polypeptide
How many cistrons does the lac operon have?
What are they?
How is the coding sequence different in prokaryotes that eukaryotes?
- -They have uninterrupted coding sequence
- -In eukaryotes exons are often interrupted by introns
- -a cluster of cistrons which are transcribed on the same mRNA
- -usually functionally related
- -coordinately regulated
- A DNA sequence that binds a repressor protein
- -located after promoter and before start codon
binds operator and blocks transcription
inducer for lac operon
- -binds to repressor
- -removes repressor from operator
USES TH EH+ ION GRADIENT TOT RANSPORT LACTOSEINTO THE CELL.
- -- GALACTOSIDASE
- -HYDROLYSES LACTOSE TO FORM GLACTOSE AND GLUCOSE.
- -makes small amount of allo-lactose
- -TRANSACETYLASE ENZYME
- -HAS UNKNOWN FUNCTION INTHE CELL
Activator in Lac-Operon
- -CRP (cAMP receptor protein) or CAP (catabolite activator protein)
- -CRP/cAMP binds to CRP site near promotor and activates transcription of Lac
What is the preferred carbon source
What are the secondary carbon sources?
Lactose and Galactose
What happens when concentration of glucose is high
- cAMP decreases
- Lac operon inactivated
What happens in high Lactose concentration?
Lac Operon active
IPTG: ind100% Hydro:0%
ONPG: ind 0% Hydro 100%
-a substrate for detection of beta-galactosidase activity. (enzyme assay)
-if β-galactosidase is present, it hydrolyzes the ONPG molecule into galactose and the yellow identifier o-nitrophenol.
- - B-D-GALACTOSIDASE SUBSTRATE
- - PRODUCES A BLUE PRECIPITATE
- -STAINS COLONIES.
- -NOT DIFFUSIBLE (DIFFUSIBLE ONPG COLOUR WOULD SMEAR BETWEEN COLONIES.)
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