How does a mutagen induce mutation? Explain with an example.

(N/A) mutagen is a physical or chemical agent that increases the rate of mutation by altering the genetic material,typically $DNA$.
$1$. Physical Mutagens: These include ionizing radiations (e.g.,$X$-rays,gamma rays) and non-ionizing radiations (e.g.,$UV$ rays). $UV$ radiation with a wavelength around $260 \ nm$ is strongly absorbed by nitrogenous bases,leading to the formation of pyrimidine dimers,which disrupt $DNA$ replication.
$2$. Chemical Mutagens: These include base analogs,alkylating agents,and intercalating agents. They can mimic normal bases or chemically modify them,leading to base-pair substitutions during $DNA$ replication.
Example: Sickle cell anemia is a classic example of a point mutation where a single base pair substitution ($GAG$ to $GTG$) in the $\beta$-globin gene leads to the replacement of glutamic acid with valine,altering the structure of hemoglobin.