An mRNA is 429 nucleotides long. The number of amino acids in the polypeptide chain formed from this mRNA is
(A) 143.
(B) 142.
(C) 141.
(D) 429.
(E) 428.



Answer :

B. 142. This is because one of the molecules has to be a stop codon which doesn't code for an amino acid. So there are only 426 nucleotides coding for the polypeptide chain. It takes 3 nucleotides to code for an amino acid. So 426 divided by 3 is 142, which is the amount of amino acids that will be part of this chain.

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