<P> When depurination occurs with DNA , it leads to the formation of apurinic site and results in an alteration of the structure . Studies estimate that as many as 5,000 purines are lost this way each day in a typical human cell . In cells , one of the main causes of depurination is the presence of endogenous metabolites undergoing chemical reactions . Apurinic sites in double - stranded DNA are efficiently repaired by portions of the base excision repair ( BER ) pathway . Depurinated bases in single - stranded DNA undergoing replication can lead to mutations , because in the absence of information from the complementary strand , BER can add an incorrect base at the apurinic site , resulting in either a transition or transversion mutation . </P>
what is the most common cause of depurination
the presence of endogenous metabolites undergoing chemical reactions