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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
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
What are polyribosomes?
One strand of mRNA being processed by multiple ribosomes at a single time
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.
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