This type of mutation occurs when one or more base pairs are added to the gene sequence.

Insertion

Explanation:

Mutation is a phenomenon in which the nucleotide sequence of a gene in DNA is changed into a new sequence due to insertion, deletion or  exchange of a gene segment.

Insertion is a type of  mutation in which one or more than pne base sequence in added into the DNA of an organism. This insertion may or may not be dangerous depending on the place of insertion and how it is causing adverse effects on the protein product of the gene.

Here is an example of insertion mutation:

Base sequence: AUG GCC TGC

Product:           met     ala      gln

Insertion:

Base sequence: AUG GCC   C TG     C

Product:              met     ala      Leu

So we can see that the product protein is changed because of insertion.

Hope it helps!