Molecular Biochem Flashcards
What are the different types of RNA?
rRNA= most abundant mRNA= longest tRNA= smallest
Rampant, Massive, Tiny
Compare prokaryotic vs eukaryotic RNA polymerases
Eukaryotes:
RNA Polymerase I makes rRNA
RNA Polymerase II makes mRNA; opens DNA @ promoter site
RNA Polymerase III makes tRNA
Prokaryotes: 1 RNA polymerase (multisubunit complex) makes all 3 kinds of RNA
Alpha-amanitin
Found in death cap mushrooms
Inhibits RNA polymerase II & causes liver failure if ingested
Name the start & stop codons
Start: AUG (methionine in eukaryotes, formyl-methionine in prokaryotes)
Stop: UGA, UAA, UAG
Origin of replication
Particular sequence in genome where DNA replication begins.
Single in prokaryotes, multiple in eukaryotes
Helicase
Unwinds DNA template at replication fork
Single-stranded binding proteins
Prevent strands from reannealing
DNA topoisomerases
Crease a nick in the helix to relieve supercoils created during replication
*Fluoroquinolones inhibit DNA gyrase (prokaryotic topoisomerase II)
Primase
Makes an RNA primer on which DNA polymerase III can initiate replication
DNA polymerase III
Prokaryotic only.
Elongates leading strand by adding deoxynucleotides to the 3’ end. Elongates lagging strand until it reaches primer of preceding fragment.
Exonuclease
3’-5’ proofreading activity in prokaryotes.
Also excises RNA primer during DNA polymerase I activity.
*Missing from Hepatitis C
DNA polymerase I
Prokaryotic only.
Degrades RNA primer and fills in the gap with DNA.
DNA ligase
Seals.
Telomerase
Enzyme adds DNA to 3’ ends of chromosomes to avoid loss of genetic material with every duplication.
Which direction does mRNA reading vs protein synthesis proceed?
mRNA: 5’ –> 3’
Protein synthesis: N to C
Shine-Dalgarno sequence
Ribosomal binding site in prokaryotic mRNA upstream from start codon
Helps to recruit ribosome to mRNA
Kozak consensus sequence
Occurs on eukaryotic mRNA. Surrounds methionine to serve as initiator for translation.
(gcc)gccRccAUGG [R = adenine or guanine]
Capped, tailed, and spliced transcript is called:
mRNA
What 3 processing steps occur in the nucleus after transcription?
- Capping on 5’ end (addition of 7-methylguanosine occurs in cytosol)
- Polyadenylation on 3’ end (~200 As)
- Splicing out of introns
snRNPs are involved in. . .
splicing of pre-mRNA
tRNA has _ _ _ at the 3’ end and binds ___
tRNA has CCA at the 3’ end and covalently binds amino acids
