Intro To Molecular Biology 4 Flashcards
Where does mRNA exit through from nucleus into membrane?
Nuclear pore
Structure of nuclear pore:
Have proteins (disordered plug) to prevent other substances accidentally getting through
Cytosolic and nuclear fibril
What does a cap-binding protein do?
Leads mRNA through pore
What does an exon-junction-complex do?
Ensure full length protein is translated
Tyopes of mutations:
Deletion
Insertion
Substitution
What is deletion?
Base pair deleted
Leads to frameshift and nonsense (changes amino acid to stop)c
What’s insertion?
Base pair inserted
Leads to frameshift and nonsense (changes amino acid to stop)
What’s substitution?
Base pair substituted/replaced with different base pair
Leads to missence mutation (amino acid changed)
What is a silent mutation?
Doesn’t change amino acid
What defines the starting point at which to read codons on mRNA?
Initiation codon
AUG = methionine
What’s the 5’ non-coding region?
Guide for machinery to start translation at AUG
What defines the ending point at which codons are read on mRNA?
Stop codon
What is the adapter between the codon and specific amino acid?
Transfer RNA
TRNA
How does tRNA bind to mRNA?
Anti-codon loop on tRNA base-pairs with codon on mRNA
How does the right amino acid get added to the right tRNA?
Aminoacyl-tRNA synthetases
Describe structure of tRNA:
Clover-leaf
Attached amino acid on 3’ end
Anticodon in anticodon loop
How does Aminoacyl-tRNA synthetase work?
Activates amino acid and ATP
Amino-acyl is added to tRNA
Activation of amino acid:
Enzyme + amino acid + ATP —-> enzyme + PPi
Transfer of amino-acyl group to tRNA:
tRNA + enzyme —-> amino-acyl-tRNA + enzyme
What does the acceptor stem do on tRNA?
Site where amino acid is added
What does editing site do on aminoacyl-tRNA synthetase?
Verifies tRNA charged with right amino acid
Large subunit on ribosome:
23s rRNA
50 proteins
Catalytic
Small subunit on ribosomes:
18s rRNA
30 proteins
Binds tRNAs
How many binding sites do ribosomes have?
One for mRNA
Three for tRNA
Three phases of translation:
Initiation
Elongation
Termination
What happens in initiation?
5’ cap structure of mRNA recognised
Ribosomes scan through 5’ non-coding region until initiation codon found
What’s required for initialisation?
Initiation factors
What happens in elongation?
Correct tRNAs bind
Peptide binds made between amino acids
What happens in termination?
Termination codon reached
Bond between protein and last tRNA is broken
Whole complex disassociates
What is required in termination?
Release factors
What’s polymorphism?
Minor change in sequence
Main cause of genetic variation
What happens after translation?
Translocation to relevant part of cell
Protein folding
Post-translational modification
Effects of mutations:
No transcription
Protein incorrectly processed
Inappropriately regulated
Inappropriate function
Unstable protein
