Mutation rate

In genetics, the mutation rate is the chance of a mutation occuring in an organism or gene in each generation. See Luria-Delbruck experiment. The mutation frequency is the number of individuals in a population with a particular mutation. This is important in fields such as evolutionary biology and oncology.

If the mutation rate of a gene is assumend to be constant (clock like) the the degree of difference between the same gene in two different species can be used to estimate how long ago two species diverged Carl Woese. In fact, the mutation rate of an organism may change in responce to environmental stress. For example UV light which damages DNA and may result in error prone attempts by the cell to repair its DNA.