Mutagens

The definition of the term mutagen is a chemical or physical agent that induces mutations. This definition is important because distinguishes mutagens from other environmental agents that cause cell damage in a way that it’s not a mutation. This mutagens definition also distinguishes between the real mutagenic agents and the agents that cause DNA damage without leading to mutations, for example agents that have as an effect DNA molecules fragmentation. This kind of damages can block replication and lead to cell death, but they’re not truly mutations, so the agents that cause this kind of effects are not mutagens.

A lot of chemicals that occur naturally in the environment possess mutagenic activities (ex. Micotoxins produced by fungi) and these mutagens have been complemented nowadays by chemical mutagens produced by human industrial activity. Beyond these chemical agents, physical agents, for example radiations, are mutagens as well. Most organisms are exposed to quantities, that can be superior or inferior, of these multiple mutagens, and so that the genomes of these organisms suffer damage. 

There can be some overlap between different categories (for example mutagens that are also carcinogens) but each one of the different types has specific biological effects. Mutagens can operate in 3 different ways:

• Some act as base analogs and what happens is that they are confused with nucleotidic bases being mistakenly used as substrates of DNA synthesis on the replication fork (Ex. 5-bromouracil).

• Some react directly with DNA, taking to structural changes that lead to miscopying of the template strand when DNA is replicated. These structural changes can be very diverse (ex. UV radiation; deamination agents; etc…).

•  Some mutagens act indirectly on DNA. This because they don’t affect directly the DNA structure, but instead induce cells to synthesize chemicals like peroxides that possess direct mutagenic activity.