JEE Main levelSingle correct optionDifficulty 2 of 3bm152
A coding region of mRNA is 300 nucleotides long and ends with one stop codon that codes for no amino acid. Assuming it starts at the first nucleotide and is read in non-overlapping triplets, how many amino acids are in the protein?
A100
B99
C98
D300
Answer: B
300 nucleotides make 300/3=100 codons. The last codon is a stop codon with no amino acid, so 100−1=99 amino acids.