Midterm #2 Material - Push to Final Flashcards
What is polycistronic?
The single mRNA carrying multiple protein-coding sequences
What is the lac operon designed for?
E.coli to break down lactose
What are the different parts of the operon?
PROG (Promoter, Repressor, Operator, Gene)
How is lactose transported?
via LacY permease
What does beta-galactosidase do?
Cleaves lactose to glucose and galactose
What happens to the operon when lactose isn’t present?
The lac operon is repressed by Lac1.
What are the independent translation control signals of an operon?
1) RBS (Ribosomal Binding Site)
2) Start Codon
3) Stop Codon
What is catabolite repression?
When a preferred carbon source is available, genes involved in the metabolism of other carbon sources is repressed.
What does the induction of lac operon require?
1) High cAMP-CRP Concentration
2) Presence of lactose
What is cyclic AMP synthesized from?
ATP via adenylate cyclase
At what type of concentrations is cAMP effective at?
very low
What does CRP stand for and what gene is it encoded by?
1) Catabolite Repressor Protein
2) crp gene
What is CRP?
A gene regulatory protein that binds cAMP
CAP Site
Region of the lac promoter (lacP) at which cAMP-CRP binds to
What is the critical parameter in gene regulation by catabolite repression?
Concentration of cAMP
What can neither crp or cya utilize?
Alternative C sources
What are the conditions when glucose is abundant?
1) low concentration of cAMP-CRP
2) Not enough cAMP-CRP to bind to lacP
3) lac operon is not expressed
What are the things lac operon induction requires?
1) Binding of cAMP-CRP to lacP
2) Absence of lacI repressor at lacO site
What is the actual inducer of the lac operon?
allolactose
What happens when there’s an absence of lactose (allolactose) or IPTG?
LacI-repressor binds to lacO, preventing transcription
Why is IPTG often used as inducer rather than lactose?
Because of its constant level
What are the advantages of plasmids?
Antibiotic resistance, toxin degradation, virulence and/or symbiosis-related functions
What do Col plasmids do?
Synthesize colicin proteins
What are colicin proteins?
Type of bacteriocin unique to E.coli strains
What are bacteriocins?
Proteins that can kill sensitive bacteria
What are R Plasmids (Resistance)?
They carry resistance to antibiotics and other factors
What are characteristics of R Plasmids?
Often broad-host-range and self-transmissible
