
DNA Sequence: The Genome Base 27
2.6 DNA Sequence Mutation and Polymorphism
While DNA replication is a high- delity process and the nucleus maintains
an army of DNA repair enzymes, sequence mutation does happen, although
at a very low frequency. In general, the rate of mutation in prokaryotic and
eukaryotic cells is at the scale of 10
− 9
per base per cell division. In multi-
cellular eukaryotic organisms, germline cells have lower mutation rate than
somatic cells. In these organisms, because most cells, including germline
cells, undergo multiple divisions in the organisms’ lifetime, the per-
generation mutation rate is signicantly higher