The sudden inheritable change in the genetic material is defined as mutation.

It is of the following types:

$(i)$ Point mutation : Mutation in single base pair which is replaced by another base pair.

A classical example of point mutation is a change of single base pair in the gene for $\beta$ globin chain that results in the change of amino acid residue glulamate to valine.

It results into a diseased condition called as sickle cell anemia.

$(ii)$ Frameshift mutation: It is a change in the reading frame because of insertion or deletion of base pair. e.g. $ATC GCT TAT A$

$(a)$ Insertion : If one or more nucleotides are added in the DNA segment it is called insertion.

If three or its multiple bases are added, they will not change the reading frame.

Infact they will form a protein with new amino acids.

$(b)$ Deletion : If one or more nucleotides are removed from the $DNA$ segment it is called deletion.

Here also, if three or its multiple bases are remove one or more amino acid from the polypeptide.