Mutagens

Mutagens are agents that increase the rate of genetic mutations by altering DNA. A mutation is a heritable change in DNA sequence. Mutagens can be chemical, physical, or biological, and may affect organisms at the cellular or organismal level.

Chemical mutagens include alkylating agents such as EMS and N-nitrosoureas that add alkyl groups to bases; base analogs like 5-bromouracil; intercalating agents such as ethidium bromide that distort the DNA helix; and platinum-based drugs that form crosslinks. Physical mutagens include ultraviolet light, which causes thymine dimers, and ionizing radiation (X-rays, gamma rays) that produce breaks and rearrangements. Biological mutagens include transposable elements that insert into new genomic locations and certain viruses that integrate into host DNA.

Mutagens increase mutation frequency through various mechanisms: damaged bases mispair during replication, DNA lesions that are misread, blocked replication, or chromosomal breaks. Resulting mutations can be point mutations, insertions, deletions, or larger rearrangements, and may be heritable if they occur in germ lines.

Mutagenicity is used in research to study gene function and to generate diversity in microbial strains. The Ames test is a common assay to screen chemicals for mutagenic potential; other tests detect DNA damage or chromosomal abnormalities. While many mutagens are linked to cancer, not all mutagens are carcinogens.

Safety and regulation: handling mutagens requires precautions to minimize exposure and environmental release.