Index >> Genetic Code

The nitrogen bases, however vary from one segment of DNA to another, so the informations might well depend on their sequences. The sequences of nitrogen bases of a given segment of DNA molecule, actually has been found to be identical to linear sequence of amino acids in a protein molecule. The proof of such colinearity between DNA nitrogen base sequence and amino acid sequence in protein molecules has first obtained from an analysis of mutants of head protein of bacteriophage T4, (Sarabhai et. al., 1964) and the A-protein tryptophan synthetase of Escherichia coli (Yanofski el. aI., 1964). The colinearity of protein molecules and DNA polynucleotides has given the clue that the specific arrangement of four nitrogen bases (e.g., A, T, C and G) in DNA polynucleotide chains somehow, determines the sequence of amino acids in protein-molecules. Therefore, these four DNA bases can be considered as four alphabets of DNA molecule.