DNA repair is happening all the time -- this is a major benefit of having double-stranded DNA. Wikipedia offers DNA damage rates of 1e3 - 1e6 DNA damage events

DNA repair is happening all the time -- this is a major benefit of having double-stranded DNA. Wikipedia offers DNA damage rates of 1e3 - 1e6 DNA damage events per cell, per day ( http://en.wikipedia.org/wiki/DNA_repair http://en.wikipedia.org/wiki/DNA_repair ). Almost all of these get repaired.