The template strand of a gene is $3^{'}$ -TACCGATTCACT- $5^{'}$ . mRNA is transcribed from it. Translation begins at the first AUG and ends at a stop codon (UAA, UAG or UGA), which adds no amino acid. How many amino acids are in the peptide?

Answer: B

mRNA is complementary:

5^{'}

-AUGGCUAAGUGA-

3^{'}

. Codons: AUG, GCU, AAG, UGA. UGA is a stop codon, so three amino acids are coded.