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What are the 4 functional domains of a tRNA molecule?
- anticodon: attaches to mRNA
- TψC arm: attaches to ribosome
- D arm: attachment site for Aminoacyl tRNA synthetase
- 3' / 5' end: amino acid binding site
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Sequence of events in translation initiation, elongation, termination
- Small ribosomal subunit binds to several initiation factors and this complex, in turn, binds to mRNA.
- This complex combines with the large ribosomal subunit, the initiation factors are released.
- Binding sites P and A are formed, the AUG codon binds to the P site.
- Second triplet dictates which tRNA molecule becomes positioned at A site
- Enzymatic reaction forms peptide bonds between these two amino acids
- Amino acid released from P site tRNA
- Each tRNA moves to the left
- a stop codon does not specify an amino acid, thus it is released from the P site without being joined to the A site AA
- Ribosome dissociates its subunits
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What are polyribosomes?
One strand of mRNA being processed by multiple ribosomes at a single time
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How many sites exists on a single ribosome and what is occuring in each site during active translation?
- E: Exit, the tRNA are released from this site
- P: Peptide, the peptide chain is attached to tRNA at this site
- A: amino acid, the next amino acid to be added to the peptide is attached to tRNA at this site.
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What effects will various mutations have on the polypeptide? deletions, additions, base substitutions, frameshift mutations
- deletitions/additions: if they aren't counterbalanced will result in a frameshift mutation
- base substitutions: will result in a missense or nonsense mutation
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