Triplet code

A triplet code is where each codon (within the code), consists of three nuceoltides. A series of experiments investigating into how certain insertion mutations and deletion mutations would affect the function of the resulting proteins that were coded for. Francis Crick led these experiments in 1961, and they were the initial evidence of the concept of a triplet code. It ruled out the idea that the nucleotides were read in overlapping reading frames, and that they were actually nonoverlapping sets of three nucleotides that would code for amino acids, starting at AUG.   

 Daniel L. Hartl, Maryellen Ruvolo (2011) Genetics: Analysis of Genes and Genomes, 8th Edition. Bartlett Publishers