Apurinic

Apurinic is a term used in molecular biology and genetics to describe a DNA base that has lost its purine base. Purines are adenine (A) and guanine (G), which are two of the four nucleotide bases in DNA. An apurinic site, also known as an AP site, is a lesion in DNA where the purine base has been removed from the sugar-phosphate backbone. These sites can arise spontaneously due to chemical degradation of the DNA or as a result of DNA damage.

The formation of apurinic sites is a common type of DNA damage that occurs naturally within cells. This damage can be caused by various factors, including exposure to reactive oxygen species, alkylating agents, and ionizing radiation. If left unrepaired, apurinic sites can lead to mutations during DNA replication, potentially causing cellular dysfunction or disease.

Cells have evolved specific repair pathways to address apurinic sites. The primary mechanism for repairing AP sites is the base excision repair (BER) pathway. This pathway involves a series of enzymatic steps that recognize and remove the baseless sugar, followed by the insertion of a new nucleotide and the re-ligation of the DNA strand. Efficient repair of apurinic sites is crucial for maintaining genomic integrity and preventing the accumulation of mutations. The study of apurinic sites and their repair mechanisms is important for understanding DNA stability and the mechanisms of mutagenesis.