Question

Please show me how you solve this from start to finish, I am having a hard time understanding this problem conceptually. Thank you.

A DNA strand consists of any sequence of four kinds of nucleotides. Suppose there were only 16 different amino acids instead of 20. Which of the following statements would be correct descriptions of the minimal number of nucleotides necessary to create a genetic code? A. 1 B. 2, provided that chain termination does not require a special codon C. 3, provided that chain termination does require a special codon D. 2, no matter how chain termination is accomplished E. Both B and C

Answer 1

Answer: Option E: Both B and C

Explanation: If the genetic code is composed of only one nucleotide then only 4 different combinations are possible because of 4 kinds of nucleotides hence, one codon is insufficient. If the genetic code is made up of 2 nucleotides, then 4 x 4 = 16 different combinations are possible which means that a maximum of 16 amino acids can be coded. Thus, if there are only 16 amino acids instead of 20 and there is no requirement for a termination codon, then 2 would be the minimum number of nucleotides required for encoding 16 amino acids, however, if termination does require a special codon, then the minimum number will be 3, since 4 x 4 x 4 = 64 combinations would be possible which means that 16 amino acids as well as extra termination codon can be encoded. Therefore, Option 'E', i.e., both B and C is the correct answer.