Q.Describe the three stages of translation — initiation, elongation and termination — at the ribosome.

AUG is the universal start codon that initiates translation and codes for methionine.

Working

In the standard genetic code, translation of an mRNA into a polypeptide always begins at a specific triplet codon called the initiation (start) codon, which is AUG. This codon is recognised by the initiator tRNA carrying the amino acid methionine (or N-formylmethionine, fMet, in prokaryotes), which is placed as the first amino acid of the growing polypeptide chain, setting the reading frame for all subsequent codons.

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Translation is the process of converting the mRNA nucleotide sequence into a polypeptide's amino acid sequence.

Gene expression proceeds in two major steps: transcription, in which the DNA sequence of a gene is copied into a complementary mRNA molecule, followed by translation, in which that mRNA is read at the ribosome in successive triplets (codons), each specifying a particular amino acid (or a stop signal) according to the genetic code; transfer RNAs bring the correct amino acids to match each codon, and these are joined by peptide bonds to build the polypeptide chain. Transcription (option b) is the earlier, DNA-to-mRNA step, not mRNA-to-protein, so it is incorrect h …