Operon Flashcards
True or false: Post-transcriptional gene regulation is wasteful
True, stores RNA to be readily transcribed for a speedy response.
true or false: Humans favour less energetically wasteful processes
False, humans are made from eukaryotic cells where it’s prokaryotic cells that favour less wasteful processes
When might we find post transcriptional gene regulation in a prokaryote
Very rare, would be used for something like fine tuning e.g. in a bacteriophage
What is the target of post transcriptional gene control
RNA
Describe pre-translational gene control factors
- most common mechanism of regulation at/before transcription
- involves variations in the RNA chain initiation and termination
- regulatory regions on the DNA and external elements solely dedicated to regulatory functions
What kind of gene control will you most commonly find in prokaryotes
Pre-transcriptional
What is the target for pre transcriptional gene control
DNA
How is gene expression controlled at the transcriptional level
The number of RNA molecules engaged in transcription is “controlled”. - transcription is done by multiple RNA molecules, the more there are the faster it’ll be transcribed
What is a promotors job on the most basic level
Determines where/if transcription is going to start
What is a Polycistronic operon
An operon (control system) that is linked to/controls a number of different genes.
- provides ones polycistronic transcript to code for multiple proteins
- usually the affects are on like an entire metabolic pathway as opposed to one protein
What is the name for the type of control provided by polysistronic operons
Co-ordinate control
Why would a gene need to be affected by positive control
Some genes have promotor regions that don’t look like typical promoter regions because they’re missing their consensus sequence, meaning that RNA won’t bind to it therefore it needs to be bound by an effector molecule to change is confirmation and allow transcription
How does positive control work
A vector molecule like an effector will bind to the promoter region and change it’s confirmation changing its shape allowing it to be read by RNA (even though the promotors not made of the correct bases)
Why would it be in a prokaryotes interest to use polycistronic operons
They’re more energy proficient and they conserve more space
Explain what negative control is
Some genes have an inhibitor/repressor bound to the operator region stopping it from being expressed.
An inducer molecule will then bind to the repressor releasing it from the gene allowing it to be transcribed
What is a constituent gene
A house hold gene, constantly switched on as it is constantly needed to keep the “household” running
True or False: some genes need to be “affected” by both positive and negative control
True, system is on when positive regulator is bound and when the inhibitor is released
What is the on-rate and off-rate
?
How can the on-rate be affected
Via modifications in RNA polymerase - bacteriophage = directed modification of bacterial RNAp to allow expression of phage genes - alternative sigma factors Changes in topology (shape) or DNA - supercoiling
What are used to reduce supercoiling
Topoisomers and helicases
