Question

Initiation of a polypeptide chain in protein synthesis is induced by?
(a) Methionine
(b) Lucine
(c) Lysine
(d) Calycine.

Answer 1

AUG is a triplet codon that codes for amino acid and also acts as an initiator codon during the synthesis of protein. An amino acid that is coded by AUG induces the initiation of a polypeptide chain.

Complete answer:
Synthesis of protein from the mRNA occurs in the translation process. In translation, polymerization of amino acids takes place to form a polypeptide. For initiation of protein synthesis ribosome binds to mRNA at the start codon that is AUG. AUG is a triplet codon that codes for the amino acid methionine. It is considered an initiator codon.

Additional Information: -DNA gets converted into mRNA during replication by a process called transcription and this mRNA is involved in protein synthesis by the translation process. Transcription and translation together are called the central dogma.
-Polymerization of amino acids to form a polypeptide is called translation
-Translational unit in mRNA is attached to the start codon (AUG) and the stop codon and codes for the polypeptide.
-For the initiation of the translation process,mRNA should be bound with ribosomes at the start codon that is AUG.which is recognized by the tRNA.
-Amino acid complexes linked to tRNA sequentially bind to appropriate codons in mRNA by forming complementary strands with tRNA anticodon.
-The triplet codon AUG has a dual function it codes for amino acid Methionine and also acts as an initiator codon.
So, the correct answer is "Methionine".

Note: -mRNA also has some additional sequences called untranslated regions (UTR) that are not translated
-They are present at both before the start codon and after the stop codon.
-Amino acid Methionine (met) is coded only by triplet codon AUG. No other codon codes for Methionine.