Mutations are genetic changes, i.e., alterations in the DNA sequence. Generally, mutations have deleterious effects, but there are exceptions where mutations may confer an adaptive advantage in a given environment. Mutations are often deleterious, and thereby these genetic changes are rare events. In consequence, mutation rates, i.e., the frequency by which new mutations arise in an organism over time, are generally very low. Finally, mutations that arise only in germ cells can be inherited from a generation to the next generation, while somatic mutations cannot be inherited.
