We note that reversion of mutated genes to ancestral forms is not totally unknown. A case in point is the recent study of reversion of mutant hothead gene in Arabidopsis thaliana to genes that existed in plants of two or more generations ago [32] . The authors have hypothesized that a template-directed restoration of ancestral DNA passed on in an RNA cache could underlie the mechanism of such reversion; the existence of such a mechanism that lies outside the DNA genome could lead to the high-frequency modification of DNA sequences in a template-directed manner, perhaps by the postulated RNA cache that could allow it to persist for several generations. While Lolle et al's RNA cache [32] would need to carry an exact duplicate of the ancestral sequence, in the case of gene sequences of the types considered here that may or may not contain intron segments and could be quite large, we could postulate existence of some as yet unknown mechanism for monitoring conformity with the overall intra-purine intra-pyrimidine base distribution pattern, as perhaps for long range correlations [7, 33] . In this connection it is also interesting to consider the possibility of the existence of some error correcting code in DNA sequences as speculated upon by Liebovitch et al [34] . They considered the DNA sequence as a digital code of four symbols and speculated that since the integrity of modern information encoding is secured by having error correcting codes built in, DNA sequences might also have such codes to allow repair enzymes to protect the fidelity of nonreplicating DNA and increase the accuracy of replication. In such a case if a linear block error correcting code is present in DNA then some bases would be a linear function of the other bases in each set of bases. Although the authors were unable to find any such simple code in the lac operon and cytochrome c gene they investigated, the suggestion remains an intriguing possibility nevertheless. Given that we are considering highly conserved genes whose functions are important to the survival of the organism, mechanisms such as these would provide a survival advantage and could be used under conditions that compromised the continued functioning of the organism or the requirements of the monitoring process.