Before revision:  We provide experimental evidence suggestive of its presence in DNA. Asymmetric cooperativity is used to explain, apart from the broken symmetries mentioned above, a number of other properties of DNA that includes four nucleotide alphabet, three nucleotide codons,  helicity, anti-parallel double-strand orientation, heteromolecular base-pairing, asymmetric base compositions, and palindromic instability  .
After revision:  Asymmetric cooperativity also leads to simple evolution-based explanations for a number of other properties of DNA that includes four nucleotide alphabet, three nucleotide codons, helicity, anti-parallel double-strand orientation, heteromolecular base-pairing, asymmetric base compositions, and palindromic instability .