Gene Regulation in Bacteria Flashcards
What are the three major bacterial morphologies?
- Spherical
- Rod- shaped
- Spiral
Why is the sigma subunit necessary for transcription of bacterial DNA?
Without the sigma subunit the polymerase 1 was initiating transcription in the wrong place.
What is bacterial transcription regulated by?
A single RNA polymerase - 5 core subunits and a regulatory subunit.
What is an operon?
An operon is a unit of genetic function. It consists of a coordinately regulated cluster of genes that result in one genetic outcome.
What is an operon composed of?
- An operator, an “on-off” switch
- A promoter
- Genes for proteins that work together
What is an operon promoter?
A specific DNA sequence recognised by RNA polymerase, RNA polymerase binds to the promoter and transcription is initiated.
What is an operon operator?
A specific DNA sequence binds to a corresponding regulatory protein. This regulator-operator complex can ‘turn a gene on or off’ by interfering with RNA polymerase activity.
What is catabolite repression?
Repression of the synthesis of a catabolic enzyme in order to use a preferred energy source first.
What affects the levels of cyclic AMP in relation to the lac operon?
Glucose levels, high glucose results in lowered cAMP, low glucose results in higher cAMP
Describe the process that results in the activation of the lac operon.
- Low glucose results in high levels of cyclic AMP
- cyclic AMP binds to CAP (catabolite activator protein), activating it
- Active CAP binds to the activator region of DNA, increasing RNA polymerase activity.
Describe the process that results in the repression of the lac operon.
- High glucose results in low levels of cyclic AMP
- Thus, cyclic AMP is not likely to bind to CAP
- Little active CAP, thus, RNA polymerase activity remains low
