Medical Genetics Also, remember that purines always hydrogen bond to pyrimidines This leaves the same distances between each pair in the middle of the dNa polymer. This reduces the likelihood that these types of mistakes are made by dna polymerase during replicationMedical Genetics Also, remember that purines always hydrogen bond to pyrimidines. This leaves the same distances between each pair in the middle of the DNA polymer. This reduces the likelihood that these types of mistakes are made by DNA polymerase during replication