Gene expression Flashcards
When do most regulations of gene expression happen?
During the level of transcription
What is the difference between cis and trans mutations affecting gene regulation?
cis mutations: Occur within the same gene and identify DNA/RNA sequences that affect regulation
trans mutations: Occur in a different gene and identify protein or RNA factors that regulate the expression of a target gene
what are the proteins/ RNA molecules that react with DNA called?
trans-acting factors
what are Cis-acting elements?
These are specific DNA sequences located near the gene they regulate. They provide binding sites for trans-acting factors
What is gene expression?
Gene expression is the process by which the information in a gene is used to make a protein. This process involves two main steps: transcription and translation. During transcription, a copy of the gene’s DNA sequence is made into RNA. During translation, the RNA sequence is used to build a protein
What are genes?
Genes are made of DNA which contains the instructions for making proteins
What are transcriptional activators?
*a type of transcription factor
They are proteins that upregulate the expression of genes
What are transcriptional repressors?
*a type of transcription factor
They are proteins that downregulate gene expression
What are inducers and corepresors in relation to transcriptional activators/ repressors?
Inducers- they bind to transcriptional factors and either stimulate the activity of transcriptional activators or inhibit transcriptional repressors
Corepressors- they bind to transcriptional factors and either stimulate the activity of transcriptional repressors or inhibit activators
What is the lac operon network?
It is a regulatory network for the expression of prokaryotic gene.
It encodes 3 proteins that function in the metabolism of lactose
What are the 3 genes found within the Lac operon network?
LacY, lacZ and lacA
What are the function of the lac operon genes?
LacZ- gene encodes the enzyme beta-galactosidase, which breaks down lactose into glucose and galactose.
lacY gene- encodes a protein called lactose permease, which transports lactose into the cell.
lacA gene- encodes the enzyme beta-galactoside transacetylase, which modifies lactose.
When is the lac operon expressed?
Only when the cell needs to metabolise lactose
Why are genes regulated at the transcription level?
Transcriptional regulation limits wasteful production of unrequired biomolecules
FOR EXAMPLE:
If a certain cell requires a specific protein, only that specific cell will make the protein rather than getting it in all cells (wasteful for those that don’t need it)
How is the expression of lac operon controlled? By what repressors gene?
It is controlled by LacI repressor gene
This is a negative control system as it ensures that the lac repressor is only produced when it is needed
What is the transcriptional activator that regulates the lac operon network?
*LacI repressor and ?
CAP- catabolite activator protein
This is transcriptional activator that stimulates transcription
POSITIVE FEEDBACK ONTROL
How does CAP work in the lac operon network?
CAP activation only works in the ABSENCE of glucose
CAP repression only works in PRESENCE of glucose
At what other level can gene expression be regulated in eukaryotes?
RNA processing
What is alternative splicing?
-Pre-mRNA splicing can occur in different patterns
-This can lead to the production of multiple proteins from the same pre-mRNA
Remember alternative splicing can involve a productive and non-productive pathway (without functional protein product) or it can lead to the production of 2 distinct proteins
At what 3 levels can gene expression be controlled?
*Don’t worry about wether its eukaryotic or prokaryotic
Transcription
RNA processing
Translation
At what stage does translation regulation occur?
Initiation
What is ferritin?
Ferritin is a FE2+ binding protein that functions in regulating the availability of cellular FE2+ levels
