W7 The Genetic Code

Question 1

tRNA binding: Wobble hypothesis

Answer 1

-tRNAs can recognise more than one codon
-First two bases (5’) of the codon bind strongly to the anticodon but there is less specificity for the 3rd base (3’)
-The base at the 5’ end of the anticodon (tRNA) can bind to multiple bases at the 3’ end of the codon

Question 2

Attaching amino acid to tRNA: Aminoacylation

Answer 2

-Charging of a tRNA
-Produces an aminoacyl-tRNA
-Aminoacyl-tRNA synthetase catalyses the reaction
-2 step reaction
-Amino acid and ATP molecule bind to specific aminoacyl synthetase enzyme

Question 3

Aminoacylation steps:

Answer 3

1) Enzyme catalyses binding of AMP to amino acid (2 phosphates lost in reaction)
2) Aminoacyl-tRNA synthetase recognises the L shaped structure of specific uncharged tRNA (D loop, anticodon loop and amino acid acceptor stem)
3) Enzyme transfers the amino acid to the tRNA (Displaces AMP)
4) Charged tRNA is discharged from the enzyme
5)

Question 4

W7 Prokaryotic Translation: