Frequency of Mutations - Mutation frequency or rate is defined as a probability of mutation per cell per generation, independent of exact physiological conditions and stage in the life cycle. Each gene probably has its own characteristic mutation behaviour. Some genes undergo mutations more frequently than others in same organism.

The mutation rate in bacteria per gene is the order of 1 mutation per 10-7 generation per cell generation. Mutation frequency of various types of spontaneous mutations depends upon the accuracy of the DNA replication machinery, efficiency of the numerous mechanisms to repair damaged DNA and the degree of exposure to various mutagenic agents present in the environment.