A coding region of mRNA is 150 nucleotides long including the stop codon. How many amino acids are in the finished polypeptide?
Answer and explanation
Correct answer: D.
- Step 1: Each codon has 3 nucleotides: 150 ÷ 3 = 50 codons. Step 2. The stop codon codes for no amino acid, so 50 − 1 = 49. **Answer: . Why not the others:** is what you get if you count the stop codon as an amino acid. is what you get if you count one amino acid per nucleotide. is what you get if you add one for the start codon.
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