Prokaryotic gene expression Flashcards
(29 cards)
The earlier the cell intervenes in the process of protein synthesis, the _______ energy it wastes. Thus, cells will tend to regulate protein synthesis _______.
less; at the earliest possible stage
Operons involved in __ are typically inducible
Catabolism
Operons involved in __ anabolism are typically repressible
Anabolic
Constitutively expressed genes are generally _
unregulated
How is the lac repressor gene expressed?
Constitutively
What is the correct order of operon elements, assuming transcription is occuring from left to right?
Promoter, operator, structural genes?
If the gene encoding the lac repressor is mutated so that the repressor can no longer bind the operator, will transcription of the lac operon occur?
Yes, because RNA polymerase will be able to bind the promoter and transcribe the operon
The TATA box is a-
sequence in the promoter region of some genes
An enhancer is
A DNA sequence several thousands on nucleotides distant from the promoter.
When bound by a protein, transcription rates increase greatly
What are the stress response elements in plants
DNA sequences
Name an example of regulation of eukaryotic transcription
Activator proteins binding to an enhancer
What is the role of the protein sigma factor?
Sigma factor recognises and binds core promoter elements and recruits RNA polymerase
How can DNA binding proteins regulate transcription (stimulate or repress)
The binding of a repressor/activator protein to a repressor/activator binding site
Allosteric Regulation-
of enzyme-catalyzed reactions allows rapid fire-tuning
Regulation of gene expression-
(regulation of the synthesis of enzymes) is slower but conserves resources
How can inducers activate repressors or activators?
Inducers bind to either repressor/activator to change it’s conformation, allowing the opposite effect to take place
Difference between inducer and constitutive proteins
Inducible promoters - synthesised only under certain conditions or on requirement Constitutive promoters - expressed all the time
What proteins are involed in the uptake and metabolism of lactose in E.coli?
B-galactoside permease - carrier protein, moves sugar into the cell
B-galactosidase - hydrolyse lactose
B-galactoside transacetylase - transfer acetyl groups to certain B-galactoside
What occurs if e.coli is grown with glucose but no lactose present?
No enzymes for lactose conversion are produced
What if lactose is predominant and glucose is low in E.coli?
All three enzymes are synthesised
What is an operon?
A cluster of genes with a single promoter that allows for genes to be co-regulated
What does an operon consist of?
A promoter, two or more structural genes and an operator
What is an operator?
a short stretch of DNA between the promoter and the structural genes
