N.E.R. N-ucleotide E-xcision R-epair.
This is the main pathway, or road map/instructions, that our body uses to repair UVB damage to DNA. This pathway functions to excise, or cut out, the incorrect nucleotides (the C's, or cytosines), and then repair the DNA strand. The steps outlined in the pic have been greatly simplified, in order to just get down the general idea...
DNA damage must first be recognized; this is pretty easy to do as the damaged section of DNA is now a mismatch to its partner strand, because it has the C nucleotides in where there should be T nucleotides. In order to be fixed, the twisted up DNA first has to be unwound in order for the mis-matched pairing section to become accessible. Now, the damaged single-stranded section is cut out. Finally, a new section is made by using the undamaged complement strand as a template by which to make the sequentially-correct complimentary strand.
But what happens if a large number of cells are damaged, as occurs in a severe sunburn? Can all of the cells get repaired? Next post!