DNA Transcription. Flashcards
Define the antisense strand?
The template for RNA synthesis.
The RNA that is synthesised will be complimentary to which strand?
To the sense strand.
Define a holoenzyme?
An enzyme that is bound to its cofactor.
Define a primary RNA transcript?
A piece of RNA that has been produced by transcription and has not been processed.
Where does translation occur?
At the ribosomes.
Where does transcription occur?
In the nucleus.
Define the sense strand?
The strand of DNA that will be identical the transcribed piece of RNA.
Will the sense strand or antisense strand of DNA be copied?
The antisense strand is copied and the sense strand is complimentary.
Define transcription?
The process of making mRNA from DNA.
Define translation?
The process of making proteins from mRNA.
What is the 1st stage of gene expression?
Transcription.
What instructions does mRNA contain?
The exact instructions of how to make a protein.
What is the template for mRNA?
DNA.
What enzyme synthesises RNA from DNA?
RNA polymerase.
How many strands of DNA will RNA polymerase use as a template?
Only 1.
In what cells can transcription and translation occur at the same time?
In prokaryotic cells.
Why can transcription and translation occur at the same time in prokaryotes?
Because both processes occur in the cytoplasm.
Does transcription and translation occur at the same time in eukaryotes?
No.
Why can’t transcription and translation occur at the same time in eukaryotes?
As transcription occurs in the nucleus.
Translation occurs in the ribosomes.
What must happen to mRNA in eukaryotes before proteins can be synthesised?
The mRNA must be finished before translation can occur.
What is a fresh piece of mRNA called in eukaryotes?
A primary transcript.
When does a primary transcript become mRNA?
After it has been processed and modified to check for any mistakes
What and where is the promoter region of a prokaryotic gene located?
It is a region of DNA located upstream of the RNA coding sequence.
What is the job of the promoter region of a prokaryotic gene?
To make sure that transcription starts at the right location.
How does the promoter region ensure that transcription starts at the right location?
By ensuring that the transcription factors bind to the correct piece of DNA.
What is the RNA coding sequence?
The sequence of DNA that is going to be transcribed to RNA.
What is the terminator region of a prokaryotic gene located and where is it located?
It is downstream from the RNA coding sequence and it contains a stop codon which will signal the end of transcription.
What is the antisense strand of DNA?
The strand of DNA that is used to synthesise the RNA. (Template strand).
Is the antisense strand read by RNA polymerase?
Yes.
How does the newly synthesised RNA differ from the antisense strand?
It is complimentary.
Meaning that if there is a G on the antisense strand then it will form a C on the RNA strand.
Newly synthesised RNA will be identical to what strand of DNA?
The sense strand.
What is the sense strand also known as?
The coding strand or non-template strand.
What is the anti-sense strand also known as?
The non-coding strand or template strand.
If the antisense strand runs in the 5 to 3 direction, what directions will the sense stand and new RNA strand run in relative to the antisense strand?
They are both identical so will run in the 3 to 5 direction.
Can both DNA strands code for proteins in transcription?
Yes.
Although only 1 DNA strand is copied, both strands can code for genes that will produce proteins.
What are the 3 stages of transcription?
Initiation.
Elongation.
Termination.
Are the sense and antisense strand interchangeable?
Yes.
What direction will RNA polymerase read DNA in?
In 3 prime to 5 prime direction.
What determines which genes are read by RNA polymerase?
The proteins that are required by the cell will determine which genes are read on which strands.
Unless stated otherwise, you should always assume that polynucleotides run in what direction?
5 prime to 3 prime.
When does the initiation stage of transcription begin in prokaryotes?
When the DNA unwinds to free up a short region of genes.
What binds to the promoter region of the template strand
Transcription factors will bind to the promoter region.
How far away is the promoter region from the start of the site of transcription?
Around -35 base pairs away
How do transcription factors recognise the promoter region?
As the region will have a specific sequence of nucleotides.
What is the sequence of nucleotides that make up the promoter region at -35 nucleotides away from the start site?
5-TTGACA-3.
What is the sequence of nucleotides that is -35 and -10 base pairs away from the start sequence known as?
A consensus sequence.
What is the region of nucleotides that make up the sequence of nucleotides at -10 nucleotides away from the start site known as?
A pribnow box.
What is the sequence of nucleotides that make up the pribnow box at -10 nucleotides away from the start site?
5-TATAAT-3
What about the consensus sequence will affect the binding of the transcription factors and the rate of transcription?
Any variation in the sequences found at the consensus sequence (-35 and -10).
What happens in the elongation stage of transcription in prokaryotes?
The RNA polymerase will synthesise an RNA molecule.
The RNA molecule that is synthesised by RNA polymerase is synthesised in what direction?
In the 5 to 3 direction.