MolBio7 - 41 Flashcards
(41 cards)
What are the 4 types of RNA?
mRNA, tRNA, rRNA, snRNA
Describe mRNA
Messenger RNA, codes for proteins, 3-5% total RNA
Describe tRNA
Transfer RNA, participates in translation, 49 families, each carries amino acid and has a specific anti-codon loop
Describe rRNA
Ribosomal RNA, major constituent of ribosomes, 4 main types
What is a stem-loop, and how is it formed?
Hair-pin RNA secondary structure caused by Watson-Crick pairing, or sometimes not - G=U can occur
Can RNA form tertiary structures?
Yes - tRNA is 3D
What is RNA polymerase?
Enzymes performing RNA synthesis
How many types of RNA polymerase are there?
3
What does RNA polymerase I do?
rRNA synthesis
What does RNA polymerase II do?
Protein-coding transcript synthesis
What does RNA polymerase III do?
tRNA, snRNA and 5S rRNA
Where does RNA polymerase bind?
Specific promotor locations
What direction does RNA synthesis proceed?
5’ > 3’
What supplementary actions does RNA polymerase also perform?
Unwinds DNA in front, re-anneals behind
What occurs to RNA transcript once transcribed?
PolyA tail added for stability and dissociation from the DNA
Name 4 core RNA promoters
TATA box, Inr, DPE, BRE
What does TBP stand for?
TATA binding protein
What does TF stand for?
Transcription factor
Which promoter does TFII bind?
Inr - initiator
Which promoter does TBP bind?
TATA box
What does BRE stand for?
TFIIB Recognition Element
Which promoter does TFIIB bind?
BRE
Outline transcription initiation
TBP binds TATA box, TFIIA binds to stabilise, TFIIB forms bridge that facilitates binding of complex to promoter, RNA polymerase binds (associated with TFIIF,G+H)
Describe the mediator complex
Huge complex, >20 subunits, binds to the C-terminal tail of RNA Polymerase II to ensure high levels of transcription
