Lysozyme is an enzyme formed from 129 amino acids. What is the minimum number of nucleotide bases required to code for this enzyme?

Lysozyme is an enzyme formed from 129 amino acids. What is the minimum number of nucleotide bases required to code for this enzyme?

• A. 129
• B. 387
• C. 258
• D. 390

Answer: (B)

Proteins are built from amino acids encoded by three-nucleotide codons. To specify 129 amino acids, you need 129 codons, and each codon is 3 bases long, so 129 × 3 = 387 bases. The stop codon isn’t coding an amino acid, so it isn’t counted when asking for the bases that code the enzyme’s amino acid sequence. If you included a termination signal, you’d add 3 bases for the stop, giving 390, but that isn’t the bases that code the amino acids themselves. The other numbers don’t fit the triplet coding scheme.

Proteins are built from amino acids encoded by three-nucleotide codons. To specify 129 amino acids, you need 129 codons, and each codon is 3 bases long, so 129 × 3 = 387 bases. The stop codon isn’t coding an amino acid, so it isn’t counted when asking for the bases that code the enzyme’s amino acid sequence. If you included a termination signal, you’d add 3 bases for the stop, giving 390, but that isn’t the bases that code the amino acids themselves. The other numbers don’t fit the triplet coding scheme.