Final answer:
Experiments with bacteriophage T4 by Francis Crick and colleagues validated the triplet code hypothesis, where insertions of three nucleotides added an extra amino acid without affecting the rest of the protein, hence defining codons as three-nucleotide sequences.
Step-by-step explanation:
Triplet Code Hypothesis
The experiments conducted by Francis Crick and his colleagues supported the hypothesis of a triplet code in genetic coding. These studies involved frameshift mutations in the bacteriophage T4, where the insertion of one or two nucleotides led to a complete change in the protein synthesis due to the alteration of the reading frame. However, the insertion of three nucleotides added an extra amino acid but did not disrupt the overall structure of the protein, indicating that codons consist of three nucleotides and that these triplet groups are the encoding units for each amino acid.
Furthermore, the concept of a commaless genetic code was proposed by Crick, which elegantly demonstrated how the ribosome reads the correct sequence of codons without needing separators or 'commas'. This was a crucial milestone in understanding genetic translation and the universal nature of the genetic code shared across various forms of life.
The genetic code's properties such as being degenerate and universal were further illuminated by these findings. The degeneracy of the genetic code reflected that a single amino acid could be encoded by multiple codons, showcasing the redundancy of the genetic code which has implications for mutation and evolution.