Question

Suppose evolution on earth has occurred in such a way that there are 96 amino acids instead of 20. DNA has 12 different types of bases and DNA synthesis occur 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

The correct option is C 2

The genetic code consists of 64 (4^3) triplets of nucleotides. These triplets are called as codons. With three exceptions, each codon encodes for one of the 20 amino acids used in the synthesis of proteins. That produces some redundancy in the code: most of the amino acids being encoded by more than one codon. One codon, AUG serves two related functions - it signals the start of translation and it codes for the incorporation of the amino acid methionine (Met) into the growing polypeptide chain. The genetic code can be expressed as either RNA codons or DNA codons. RNA codons occur in messenger RNA (mRNA) and are the codons that are actually "read" during the synthesis of polypeptides. But each mRNA molecule acquires its sequence of nucleotides by transcription from the corresponding gene. Because DNA sequencing has become so rapid and because most genes are now being discovered at the level of DNA before they are discovered as mRNA or as a protein product, it is extremely useful to have a table of codons expressed as DNA. So here are both. So, if evolution on earth has occurred in such a way that there are 96 amino acids instead of 20. DNA has 12 different types of bases and DNA synthesis occur in the same way as today. The minimum number of bases per DNA codon would be 2 (12^2=144) in all the time. Thus, option C is correct.