Self-correcting mutations


This is an idea I first wrote in my private files several years ago:

 

It is commonly assumed that mutations are either corrected right away by a DNA polymerase with proofreading ability that detects a mismatch between bases in a base pair during replication, when one strand is still incipient and thus a clear asymmetry exists between template and copy, or become incorporated forever. Yet biology could easily detect a mutation even in a 'mature' double-stranded helix and correct it when this is evolutionary advantageous. In homozygous loci of organisms with paired chromosomes, biology could look at the corresponding gene in the corresponding chromosome to detect which of two mismatched bases is the mutant. Even in a single chromosome, base-age-dependent physico-chemical modifications such as sugar coating could distinguish original bases from recently mutated ones.