Question

Suppose, Evolution on earth had occurred in such a way that there are 96 amino acids instead of 20. DNA has 12 different types of bases and DNA synthesis occurs in the same way as today. The minimum number of bases per DNA codon would be

• A. 12
• B. 8
• C. 2
• D. 3

Answer 1

Answer: (C)

There are 4 nitrogen bases which are used for the formation of DNA and RNA. There are codons in the mRNA. There are three nucleotides out of 4 bases are arranged in triplets (codons) which will encode for the amino acids. There are 20 amino acids. So, 4${}^3$= 64. There are 64 codons which code for 20 amino acids.

If there are 12 nitrogen bases which are used for the formation of DNA and RNA. Then 12 bases need to be arranged in triplets (codons) which will encode for the 96 amino acids. So, 12${}^2$= 144. There are 144 codons which code for 96 amino acids from 2 bases in each codon.

Thus, the correct answer is option C.