DNA Transcription Flashcards
This is the process by which information from a gene is used in the synthesis of a functional gene or product: protein or non coding RNA
a) transcription
b) translation
c) gene expression
d) DNA replication
Gene expression
This states that genetic information only flows in one direction. (from DNA to RNA via transcription and from RNA to proteins via translation)
Central Dogma of Molecular Biology
Why is the Central Dogma of Molecular Biology wrong?
Because RNA can be used to make new DNA
Because DNA can give rise to non-coding RNA (which does not code for a functional protein)
Genetic information doesn’t just go one way.
This is an RNA molecule that does not give rise to a protein and has some other function
Non-coding RNA
A defined region (sequence) of DNA that produces a type of RNA molecules that has some function
Gene
What are 3 functions of a gene sequence?
Regulating synthesis of RNA
Produce RNA
Further process RNA
This is a DNA-dependent RNA synthesis.
Transcription
What is the enzyme used to catalyse transcription?
RNA polymerase
How does RNA polymerase synthesise mRNA?
By catalysing the formation of phosphodiester bonds between ribonucleotides.
mRNA is transcribed from which strand?
Template strand
What is the template strand?
The DNA sequence that is to be transcribed. The strand that determines what base will be added complementary to it. Template strand is synthesised in 3’ to 5’ direction
What is the coding strand?
The strand that RNA polymerase will add nucleotide bases to. Coding strand is synthesised in 5’ to 3’ direction.
What are the 3 stages of Transcription?
Initiation, Elongation, Termination
Initiation is regulated by specific DNA sequences. What is an example of this?
TATA box and promoter regions to initiate mRNA synthesis.
Does transcription require a primer? Why/why not?
No it does not need a primer.
It has promoter regions that contain a TATA box that transcription factors will bind to for the RNA pol II to bind to and start transcription.
What is the enzyme responsible for forming a transcriptional initiation complex? What does it bind to?
RNA polymerase II binds to transcription factors on the TATA box (in promoter regions)
These are regions of the DNA sequence that can be transcribed but not translated.
They are involved in regulating gene expression.
Non-coding regions
What happens if there are mutations in non-coding regions?
This results in disruption of normal gene expression
This is a DNA segment that is recognised by RNA polymerase to initiate transcription.
Promoter regions
These contain regulatory elements/sequences that influence on gene expression at transcriptional/translational level
UTRs/untranslated regions like 5’ UTR 3’UTR
This facilitates the addition of Poly A tail
3’ UTR
This facilitates the addition of 5’ G cap
5 ‘ UTR
This prevents the degradation of mRNA and facilitates export of mRNA from nucleus to cytoplasm.
Poly A tail
This is the process where introns are removed to form a full coding sequence using UTRs
Splicing
Where does transcription occur in eukaryotes?
In the nucleus
Where does transcription occur in prokaryotes?
In the cytoplasm
Which parts of a gene are transcribed from DNA to mRNA?
Coding sequence + non-coding regions (like UTR)
Which parts of a gene are translated from mRNA to proteins?
Coding sequence only
