What is an Apurinic site?
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.
Which nucleotide is most often inserted opposite an Apurinic site during DNA replication?
T
During the next round of DNA replication, the most likely base to be inserted opposite to the AP site is A [101]. When the coding strand of the DNA is then replicated, a T is inserted opposite to the new A. This results in the G to T transversion.
How are Apurinic sites repaired?
In wild-type cells, AP sites are primarily repaired by the base excision repair (BER) pathway, with the nucleotide excision repair (NER) pathway as a back up activity.
What causes depurination?
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.
What is Apurinic acid?
A DNA derivative in which all the purine bases have been removed by selective hydrolysis, leaving the pyrimidine‐deoxyribose bonds and the phosphodiester bonds of the backbone intact. It results from the gentle acid hydrolysis of DNA at pH 3.0.
How are abasic sites repaired?
Briefly, the five major steps are: recognition and removal of incorrect or damaged DNA base, excision of AP site by AP endonuclease or AP lyase, cleaning up of DNA ends, repair synthesis by DNA polymerase, and sealing of the nick by DNA ligase.
What is an example of good mutation?
Mutations can be beneficial, benign, or malignant, depending on where in the genetic code they are located. Examples of beneficial mutations include HIV resistance, lactose tolerance, and trichromatic vision.
What is the difference between mismatch repair and nucleotide excision repair?
The main difference between mismatch repair and nucleotide excision repair is that mismatch repair (MMR) is responsible for the removal of base mismatches and small insertion/deletion loops introduced during DNA replication, whereas nucleotide excision repair (NER) is responsible for the removal of a variety of DNA …
What is a bulky adduct?
Bulky DNA adducts are markers of exposure to genotoxic aromatic compounds, which reflect an individual’s ability to metabolically activate carcinogens and to repair DNA damage. Polycyclic aromatic hydrocarbons (PAH) represent a major class of carcinogens that are capable of forming such adducts.
What happens in depurination?
Depurination involves the loss of purine bases (adenine and guanine) from DNA. In spontaneously occurring depurination reactions, the N-glycosyl bound to deoxyribose is broken by hydrolysis, leaving the DNA’s sugar–phosphate chain intact, producing an abasic site.