Answer to Question #171017 in Genetics for Sam

Question

Explain why the genetic code would not work if nucleotide bases were arranged in pairs rather than in triplets, to make the coding units.

Answer 1

The reading of code in pairs of nucleotides is insufficient since only 16 different combinations (4²) of the four nitrogenous bases can be made. Given that there are 20 amino acids, 16 different combinations would not suffice.

Each group of three nucleotides encodes one amino acid. Since there are 64 combinations of 4 nucleotides taken three at a time and only 20 amino acids, the code is degenerate (more than one codon per amino acid.