What is a mutagen?

A mutagen is an agent that causes changes to the DNA sequence, leading to mutations. These changes can occur in various ways, such as by altering the structure of DNA or introducing errors during DNA replication. Mutagens can be physical (like radiation), chemical (such as certain substances in tobacco smoke or industrial pollutants), or biological (like some viruses). Understanding what a mutagen is is crucial because it highlights the mechanisms through which genetic variations can occur, impacting biological diversity and evolution. In contrast, the other options describe different concepts unrelated to the effect of mutagens on genetic material. For example, a drug that cures mutations would imply healing pre-existing mutations rather than causing them, a genetic disorder describes a condition resulting from mutations rather than the mutagens themselves, and a natural response to stimuli pertains to behavioral or physiological responses, not changes in genetic material.