"Sometimes during DNA replication a change in the DNA nucleotide sequence, which is called a mutation, can occur. There are various reasons why mutations occur. In certain instances, a chemical called can increase the mutation rate."

Mutagen

There are various reasons why mutations occur. In certain instances, a chemical called mutagen can increase the mutation rate."

Explanation:

A mutagen is a chemical agent that changes the genetic material, usually DNA, of an organism and this increases the frequency of mutations above the natural background level.

Other causes of mutation include:

- error in DNA replication, repair and recombination