Question

Question:The codons in the genetic code are sequences of three bases. Explain why sequences of only two bases could not be used to code for the 20 different amino acids commonly found in proteins.

Short answer

Instead of two (2) bases, the three (3) bases are used in twenty amino acids because they give sixty-four possible combinations.

Step-by-step solution

Genetic coding.

The sequence of bases in the coding strand of deoxyribonucleic acid (DNA) or a messenger ribonucleic acid (RNA) as coded instructions for building protein chains out of amino acids. Twenty (20) amino acids are used in protein formation, but only four different bases are used to code for them. Only one base cannot code for one amino acid. That would leave sixteen (16) amino acids with no codes.

The three bases used to code twenty amino acids.

Suppose we take two bases to code for each amino acid. That would still only give us sixteen (16) possible combinations $(4\times 4)$, which is not enough. While, if we take three (3) bases for each amino acid, that form sixty-four (64) possible combinations $(4\times 4\times 4)$. That is enough to code for every amino acid with lots of spare.