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15 Cards in this Set

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What are the 5 important features of the genetic code?
1) read 5' to 3' (N to C terminus)
2) read in triplets (codons)
3) nonoverlapping
4) not punctuated
5) unambiguous
What are the 2 most important parts of the tRNA?
- anticodon loop
- acceptor stem (amino acid is attached)
What are the 3 steps of translation?
1) initiation
2) elongation
3) termination
What are the 3 steps of elongation?
1) Binding of specific tRNA to A site (added from A to P direction)
2) Peptide bond formation (via peptidyl transferase)
3) translocation of mRNA and peptidyl tRNA moves from teh A to the P site and the tRNA in the P site is removed
repeat
What happens in initiation?
- mRNA binds to the 2 halves of the rRNA and recruits tRNA with fMet (goes into P site)
What happens in termination?
- nonsense/stop codon enters A site
- release factor catalyzes the addition of a water molecule to the peptide chain which hydrolyzes the bond that holds the chain to the last tRNA
What is the wobble hypothesis?
- certain flexibility in binding of tRNA to ribosome-mRNA at the third codon position
- inosine often used in tRNA 3rd position
What are 7 examples of post-translational modifications?
1) protein folding
2) protein/protein interactions
3) remove N-terminal methionine
4) removal of signal sequences in ER
5) glycosylation secreted proteins in golgi
6) ubiquination (targets for degradation in proteosome)
7) phosphorylation/ acetylation/methylation/biotinlation
How does tetracycline work?
- inhibits binding of aminoacyl tRNA to ribosome
- inhibits elongation
How does streptomycin work?
- inhibits initiation and causes misreadings of mRNA
- inhibits initiaiton and elongation
How does chloramphenicol work?
- inhibits elongation by acting as a competitive inhibitor of peptidyltransferase activity (can't form bonds)
How does erythromycin work?
- blocks translocation step in chain elongation
How does puromycin work?
- premature chain termination by acting as an analog of aminoacyl-tRNA
What are the 3 mutations that were discussed?
1) missense (replaces codon for one amino acid with codon for a different one)
2) nonsense (replaces codon for amino acid with stop codon)
3) frameshift (adds/subtracts nucleotides not in steps of and changes reading frame)
How do secreted proteins get targeted for surface?
- secreted proteins have hydrophobic area (signal peptide) that is recognized by signal recognition particle (ribonuclear complex)
- complex docks on peptide and requires ribosome that is translating the peptide to dock on the ER
- peptide is complete it is folded in ER
- goes to golgi->vessicle->cell surface