Compare and contrast base excision repair and nucleotide exe

Compare and contrast base excision repair and nucleotide exes, on repair.

Solution

Base excision repair ( BER) and Nucleotide excision repair are two methods of repairing damaged DNA , mostly employed by prokaryotes. The basic differences both the methods can be summarized as -

The BER employs an enzyme called as DNA glycosylase, AP endonucleases, AP lyase, pol and DNA ligase XRCC1.Modified or damaged base is removed by a DNA glycosylase (several glycosylases have been described, including uracil -DNA glycosylase), creating an apurinic or apyrimidinic (AP) site.• AP- deoxyribose is then released by AP exonucleases. Missing nucleotide replaced by DNA polymerase and ligated.

NER removes diverse, bulky lesions caused by UV induced damage. The general steps include Damage recognition, Binding of a multi-protein complex at the damaged site, Double incision of the damaged strand several nucleotides away from the damaged site, on both the 5\' and 3\' sides, Removal of the damage-containing oligonucleotide from between the two nicks, filling in the gap by DNA Polymerase, and finally ligation.

Type of repair	BER	NER
size of chemical group added in the damage event it repairs	small adducts	large adducts
does the damage it repairs distort the DNA helix?	non-distorting	distorting
repairs damage caused by	endogenous mutagens	exogenous mutagens
recognizes	specific chemical changes	general damage