The correct answer is: 5) NER recognizes helix distortions, while BER recognizes specific base damage.
DNA damage that occurs as a result of radiation, oxidizing reagents, chemicals and other mutagens can be repaired. Excision repair repairs single strand DNA damage and it includes:
• Nucleotide excision repair (NER)-it detects and repairs types of damage that distort the DNA double helix such as those of UV radiation (thymine dimers); not only the damaged nucleotide(s) are removed but also a surrounding patch of DNA
• Base excision repair (BER)-it detects and removes certain types of damaged bases (small, non-helix-distorting bases); enzyme glycosylase is responsible for this type of repair
