Question

A messenger RNA is 339 bases long including the initiation and termination codon. The number of amino acids in the polypeptide translated from this is ________.

• A. \( 110 \)
• B. \( 112 \)
• C. \( 660 \)
• D. \( 666 \)

Hint:

Always remember to subtract exactly one stop codon from the total codon count when calculating protein length!

Answer 1

The Correct Option is B

Concept: The translation process converts the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis.
• Genetic code is a triplet code (3 bases = 1 codon).
• Each codon represents either one amino acid or a signal to stop translation.

Step 1: Calculating total codons.
Total bases = 339. Since each codon is 3 bases long: \( \text{Total Codons} = \frac{339}{3} = 113 \text{ codons.} \)

Step 2: Accounting for Start and Stop signals.
The initiation (Start) codon (AUG) codes for the first amino acid (Methionine). The termination (Stop) codon does not code for any amino acid; it only signals the end of the chain. \( \text{Number of amino acids} = \text{Total codons} - \text{Stop codon} \) \( 113 - 1 = 112 \text{ amino acids.} \) Final Answer: The number of amino acids in the translated polypeptide is 112.