Question

A messenger acid is 336 nucleotides long, including the initiator and termination codons. The number of amino acids in the protein translated from this mRNA is

• A. 999
• B. 630
• C. 330
• D. 111

Answer 1

Answer: (D)

111

mRNA or messenger RNA is a ribonucleic acid molecule coded by DNA. This mRNA is read by ribosome and protein is synthesized. The bases on mRNA are read in triplets and this group of 3 bases is known as codons. Every protein synthesis starts with START codon or initiator codon AUG. Similarly, protein synthesis always ends on a STOP codon or a terminator codon, UAA, UAG, or UGA. Every codon except the STOP codons codes for an amino acid.

So here in a 336 nucleotide long mRNA, there will be total 336/3=112 codons.

All codons except stop codons code for an amino acid, so there will be a total of 111 amino acids in the protein translated from this mRNA.

Hence the correct answer is D.