Question

Explain the steps involved in translation

Answer 1

During translation, the genetic information present in mRNA directs the order of specific amino acids to form a polypeptide chain. The main steps in translation are :

1) Activation of amino acids- Amino acid is activating by an enzyme called Amino Acyl tRNA Synthetase.

2) Transfer of amino acids to tRNA

3) Initiation of the polypeptide chain synthesis - the smaller ribosomal unit attaches to mRNA to form mRNA smaller subunit complex. Most often the starting amino acid is methionine in eukaryotes and N-formyl methionine in prokaryotes. The activated amino acid tRNA complex attaches initiation codon AUG on mRNA to form smaller subunit complex. The larger subunit then joins this smaller subunit initiation complex to form a complete initiation complex.

4) Elongation of polypeptide chain - second amino acid tRNA complex now occupies the A site of larger ribosomal units. Peptide bond formation takes place between both the amino acids present at P-site as well as A-site. The enzyme helps in peptide bond formation is Peptidyl transferase. After peptide bond formation translocation occurs, which involves the movement of the second amino acid and tRNA complex from A-site to P-site.

5) Termination of chain synthesis - termination codon provides signals to the ribosomes for attachment of the release factors. The release factors interact with the peptidyl transferase causing hydrolysis of a bond between tRNA and polypeptide chain and the chain is released from the ribosome. Hydrolysis of GTP results in dissociation of release factor from the ribosome.