Based on occurrence:

a) Spontaneous mutation:

• It occurs suddenly and its origin is unknown. It is reported in nature in many cases such as bread mold, microorganism , mice, human, etc.

b) Induced mutation:

• Mutation can be induced artificially by exposing the organism to abnormal environment such as; radiation, change in temperature, chemicals , etc. They also called mutagens.

Based on origin:

a) Gene mutation:

• It is defined as the change in structure of the individual gene or in the cistron of the DNA molecule. It is occur by following two types of changes in the DNA and RNA.

i) Fame-shift mutation:

The mutation caused by the addition or deletion of nitrogenous bases in the DNA or mRNA. One deletion is neutralized by one addition or vice-versa namely, addition mutation and deletion mutation.

ii) Substitution mutation:

Here, one base pair replaced by a different one. It is of two types transition and transversion.

b) Chromosomal mutation:

It is caused either by the change in structure of chromosomes called chromosomal aberrations or by the change in number of chromosomes known as genomatic mutation or ploidy.

i) Chromosomal aberrations:

It is most likely to occur during mitosis or meiosis. Large pieces of chromosomes may break of and be lost, or in wrong place. These are of different types namely, deficiency, deletion, duplication , inversion and translocation.

ii) Genomatic mutations or ploidy:

It is caused by change in number of chromosomes. These are also of different types namely, aneuploidy and euploidy.

Based on the direction of mutation:

1. Forward mutation: From wild type allele to a mutant allele.
2. Reverse mutation: From a mutant allele to the normal allele.

Based on dominance relationship:

1. Dominant
2. Recessive
3. Co-dominant
4. Partially dominant mutation.

Based on effect of survival:

a) Lethal: Kills the individual at homozygous state.

b) Sub lethal: Kills more than 50% individuals.

c) Sub vital: Kills less than 50% individuals.

d) Vital: Generally, no effects

e) Super vital: Enhance the effects.

Based on magnitude of phenotype effect:

a) Micro mutation

b) Macro mutation