where 3 is the number of base pairs that make up a codon. The information I 1 forΣn 6 is of the protein coding sequences, because it is just the length of protein coding genes in bits. The information I 2 for log(x!) is of regulatory sequences. The x should be the number of protein linkage groups or operons. If all virus proteins are in one operon or linkage group or expressed simultaneously, no regulatory information is necessary. Because the number of protein linkage groups is usually unknown, we still use the number of proteins instead. The real I 2 in viruses is very possibly equal to x log(x) because in this way viruses can use fixed length of regulatory sequence log(x) for every gene or operon. This may simplify the mechanism of regulation. Although the information I 2 is calculated by assuming one by one protein expression, the result is that each gene or operon has a regulatory sequence, which is very possibly true.