(During or prior to start of 5'-3' exonuclease activity) How does DNA Pol I decide that the coming nucleotide is of RNA not of DNA??? As we know everytime every nucleotides of RNA primer are not "U", sometimes or most of the times these may be " A, G & C". So please tell me after chewing the RNA primer, how Pol I decide to stop its 5'-3' exonuclease activity???? [Think of Replication as well as lagging strands)