Answer to Question 3 from December, 2003

3. List the steps of nucleotide excision repair (NER) that are common to bacteria and eukaryotic organisms. Do not list any steps that are specific to bacteria or eukaryotes, and do not use specific protein/enzyme names. I'm looking for a simple description of the basic steps of NER (6 points).

I gave full credit for answers that included the following steps:

• Recognition of DNA damage by a heteromeric protein complex
• Recruitment of additional proteins to the damaged site
• Cutting of the damage-containing DNA strand on each side of the damage
• Unwinding of the double-stranded DNA in the vicinity of the damage
• Release of the damage-containing oligonucleotide
• Filling in of the resulting gap by a DNA polymerase, using the complementary (undamaged) strand as template
• Ligation of the final nick.

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