Amino acid residues are classified in many groups such as hydrophobic, polar, charged, etc. Nevertheless, these groups are not saying any uniqueness under statistical results. Different classifications have different statistical results. Many of the groupings of amino acid residues analyses are not related to Chargaff’s rule. But the nucleotide favorable amino acid grouping is unique under statistical calculation. It is also related to the Chargaff’s rule of protein nucleotide content. The basis of present explanations of the manner in which the amino acids are activated before being assembled to make a protein; they are being invoked incessantly in attempts to unravel the nucleotide code which is thought to be responsible for specifying the amino acid sequence of proteins. Finally, we observed that the parity ratio of protein sequences ranges between 0.96% and 1.04% for most of the protein families. The +0.04% variation may be rectified from the alignment of the sequencing. The difference between the parity ratio of these families of protein sequences and the unity of Chargaff rule range from –0.3 to +0.3. We propose that the protein parity ratio for nucleotide favorable amino acid grouping has similar statistical calculation in all protein sequences. This statistical calculation is similar to Chargaff’s rule. The approach proposed in the present paper may be further pursued to show how different classifications of amino acids can complement each other to yield the properties of extant protein sequences.
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