A mutation is a spontaneous change in the DNA
sequence within the gene that may lead to a change in the trait which
it codes for. Any change in a single base pair may lead to a
corresponding change in one or more of the amino acids for which it
codes, which can then change the enzyme or cell structure that
consequently changes the affinity or effective activity of the targeted
In prokaryotic genomes, mutations frequently occur due to base changes caused by exogenous agents, DNA polymerase errors, deletions, insertions and duplications. For prokaryotes, there is a constant rate of spontaneous mutation of about 0.0033 mutations per DNA replication that is relatively uniform for a diverse spectrum of organisms. The mutation rate for individual genes varies significantly among and within genes (Gillespie, 2002).