Flashcards in Molecular Biochem Deck (21):
What are the different types of RNA?
rRNA= most abundant
Rampant, Massive, Tiny
Compare prokaryotic vs eukaryotic RNA polymerases
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
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
Unwinds DNA template at replication fork
Single-stranded binding proteins
Prevent strands from reannealing
Crease a nick in the helix to relieve supercoils created during replication
*Fluoroquinolones inhibit DNA gyrase (prokaryotic topoisomerase II)
Makes an RNA primer on which DNA polymerase III can initiate replication
DNA polymerase III
Elongates leading strand by adding deoxynucleotides to the 3' end. Elongates lagging strand until it reaches primer of preceding fragment.
3'-5' proofreading activity in prokaryotes.
Also excises RNA primer during DNA polymerase I activity.
*Missing from Hepatitis C
DNA polymerase I
Degrades RNA primer and fills in the gap with DNA.
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
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:
What 3 processing steps occur in the nucleus after transcription?
1. Capping on 5' end (addition of 7-methylguanosine occurs in cytosol)
2. Polyadenylation on 3' end (~200 As)
3. Splicing out of introns
snRNPs are involved in. . .
splicing of pre-mRNA