RNA Flashcards
mRNA and tRNA are synthesized where?
nucleoplasm
rRNA is synthesized where?
nucleolus
Start codon codes for what amino acid (eukaryotes)
methionine (AUG)
in prokaryotes –> formylmethionine
Stop codons
UGA
UAA
UAG
These bind to promoter regions in order for transcription to take place
Transcription factors
Promoter regions:
- 75 CCAAT box (75 nucleotides upstream)
- 25 Hogness/TATA box
- 10 Pribnow/TATAAT box
Function of operator region:
Binds repressor or inducer
between promoter region and start site
RNA polymerase I function
rRNA synth
RNA polymerase II
mRNA synth
RNA polymerase III
tRNA
alpha-amanitin toxicity?
inhibits RNA polymerase II –> hepatotoxicity
Prokaryote RNA Polymerase inhibited by what drug?
Rifampin
Processing hnRNA is required for RNA to:
leave nucleus through nucleopores
mRNA is produced from hnRNA by doing these steps:
Cap 5’end
Polyadenylate 3’ end
Removing introns
The 5’ cap in mRNA is what chemical
7-methyl-guanosine
provided by S-adenosyl-methionine or SAM
In mRNA synthesis the 3’ end is polyadenylated by what enzyme
poly-A polymerase
Codon sequence that initiates polyadenylation of 3’ end of mRNA
AAUAAA
What amino acid frequently has more coding sequences in mRNA than are represented in peptide that is created from the mRNA?
methionine
Start codon AUG in mRNA results in initial methionine which is cleaved off
What two factors regulate the lac operon ?
CAP (catabolite activating protein)
lac repressor
lac operon: Allows RNA polymerase to bind to the DNA, which in turn allows transcription of B-galactosidase gene
CAP
only binds to DNA if glucose is present
lac operon: prevents RNA polymerase from binding to DNA
lac repressor
Bound to lac operator region unless lactose is present
(lactose binds to lac repressor –> lac repressor released from DNA –> transcription can occur)
