Question Detail
Question
The insulin molecule is composed of two polypeptide chains, one consisting of 20 amino acids and the other consisting of 31. What is the minimum number of base pairs of DNA required to code for this molecule?
Correct Answer
Option D is the correct answer.
Detailed Explanation
Total amino acids = 20 + 31 = 51. Each amino acid is coded for by a codon of 3 nucleotides (a triplet) on the mRNA. Therefore, the mRNA requires 51 * 3 = 153 nucleotides. Since DNA is double-stranded, the number of base pairs in the DNA that codes for this mRNA is equal to the number of nucleotides in the mRNA (because one strand of DNA is the template). Therefore, the minimum number of base pairs is 153.
Hint
Remember the genetic code is a triplet code. How many bases code for one amino acid?