Molecular Basis of DNA Transcription Flashcards
What is transcription?
The process of mRNA synthesis during protein synthesis.
What is translation?
The process of protein synthesis from mRNA during protein synthesis.
Is the template strand of DNA complimentary to or the same as the RNA produced in transcription?
Complementary to the RNA produced.
Is the coding strand of DNA complimentary to or the same as the RNA produced in transcription?
The same as the RNA produced.
Name X3 ways in which RNA differs from DNA.
It is a single strand (DNA is double stranded)
It’s sugar is ribose (not deoxyribose)
Thymine is replaced by uracil
Which enzyme unravels DNA during transcription?
RNA polymerase.
What are the X3 main steps of transcription?
Initiation
Elongation
Termination
What direction does the mRNA synthesise from/to?
From the 5-prime to the 3-prime (of the mRNA being synthesised)
What does UTR stand for in relation to mRNA regions.
Untranslated region.
How many UTR regions does a strand of mRNA have?
X2
A 5-prime UTR and a 3-prime UTR
What is the name of the -10 box at the promoter site of prokaryotic DNA?
Pribnow box
What binds to the pribnow box and allows RNA polymerase to anchor to it in order to begin transcription?
Sigma factor
Which two boxes interact with RNA polymerase in the transcription of prokaryotic DNA?
- 10 box (pribnow box)
- 35 box
What is the sequence of DNA bases that make up the pribnow box?
TATAAT
What is the name of the box in the promoter region of eukaryotic DNA?
TATA box
What name is given to the equivalent of sigma factors (in prokaryotes) in eukaryotic DNA promoter regions which aids positioning and binding of RNA polymerase for transcription?
Transcription factors
How many base pairs long is the DNA-RNA helix during the elongation phase of transcription and roughly what is its speed in nucleotides/second?
12bp in length
Speed = 50 nucleotides/second
What does the mRNA form when it reaches the transcriptional termination site in order to halt synthesis?
A G-C rich “stem loop” in which the base pairs pair together (forming the loop hence the name)
What is splicing?
The removal or introns from hnmRNA to form mature mRNA including only exons.
Why is mRNA capped?
It aids binding of the mRNA to ribosomes.
What molecule caps mRNA?
7-methylguanosine
Explain the bond formed in the capping of mRNA.
It is a 5-prime to 5-prime bond via a triphosphate bridge.
What is polyadenylation?
The addition of 50-250 adenosine residues to the 3-prime end of the mRNA to provide it with stability.
What is the name of the process whereby 50-250 adenosine residues are added to the 3-prime end of the mRNA to provide it with stability.
Polyadenylation
What is the difference between coding and non-coding RNA, and give examples of each.
Coding = transcription and transcribed into a protein
*mRNA
Non-coding = transcripted into RNA from DNA but NOT translated into a protein.
- tRNA (transfer)
- rRNA (ribosomal)
- miRNA (micro)
Which type of RNA polymerase does mRNA use?
RNA polymerase 2
Which type of RNA polymerase does rRNA use?
RNA polymerase 1
Which type of RNA polymerase does tRNA use?
RNA polymerase 3
What is the consequence of methylation/un-methylation on DNA?
Methylated DNA = genes “switched off”
Un-methylated DNA = genes “switched on”
Does acetylated histones mean that a gene is switched on or off?
On
Does deacetylated histones mean that a gene is switched on or off?
Off
