Translation 1 Flashcards
Why is the genetic code triplet?
There are 20 types of amino acid and 4 bases, meaning the code must be at least triplet.
Why is the genetic code degenerate?
There is a redundancy and some amino acids are encoded by more than one codon.
Is the redundancy in the genetic code random?
No- it is always in the 3rd base of a codon.
Why is the redundancy in the genetic code always in the 3rd base of a codon?
Due to wobble base pairing- between the 3rd base of the codon and the 1st base of the anticodon of tRNA. This is because of modified bases in the tRNA.
How did Crick and Brenner show that the genetic code was triplet?
By mutational analysis.
What was Nirenberg’s experiment?
Adding synthetic polynucleotides to bacterial extracts and showed they could make polypeptides.
How was the genetic code deciphered?
- Synthesis of all triplet combinations, bound with ribosomes on an assay.
- Identification of the amino acid produced by each combination.
How are amino acids joined to tRNA molecules?
At the 3’ end of tRNA.
Describe the structure of tRNA.
L-shaped with the anticodon at one end and the amino acid at the other.
Folded on itself due to intramolecular base pairing.
Base stacking due to stem loop stacking.
Where are modified bases found in tRNA?
The D arm and the TWC arm.
Where are the variable regions in tRNA?
Bases in the anticodon and the extra arm.
What is tRNA charging?
The covalent linkage of amino acids to tRNAs.
How do tRNAs bind to the correct amino acid?
Aminoacyl tRNA syntetases can recognise subtle differences in amino acid structure.
What happens if a tRNA is mischarged?
tRNA synthetases has proof reading activity and will hydrolyse the incorrect amino acyl- tRNA bond.
What is the size of a ribosome?
~18nm in diameter.
