In
biochemistry and
molecular genetics, an
AP site (
apurinic/apyrimidinic site), also known as an
abasic site, is a location in
DNA (also in
RNA but much less likely) that has neither a
purine nor a
pyrimidine base, either spontaneously or due to
DNA damage. It has been estimated that under physiological conditions 10,000 apurinic sites and 500 apyrimidinic may be generated in a cell daily.