Mismatch Repair Implies Chargaff’s PR2 For Nucleus DNA

Chargaff’s second parity rule (PR2) holds empirically for most types of DNA that along single strands of DNA the base contents are equal for complimentary bases, A = T,G = C. A Markov chain model is constructed to track the base evolution of any position along template strands of DNA whose replication is equipped with mismatch repair. Under the key assumptions that the mismatch error rates primarily depend on the complementarity and the steric effect of the nucleotides and that the mismatch repairing process itself makes strand recognition errors, the model shows that the steady state probabilities for the base position to take on one of the 4 nucleotide bases are equal for complimentary bases, and that PR2 is the result of the law of large numbers acting on the base’s steady state distribution.