Mutagen

From EvoWiki

A mutagen is a chemical substance or wavelength of radiation that increases the rate of mutation above the background level causes by spontaneous mutations.

Examples of Mutagens

There are some very common mutagenic agents, listed below:

Ultraviolet light: UV light is a component of natural sunlight, but is also a mutagen in all organisms. Pyrimidines (usually Thymine) that are adjacent in the DNA absorb the light energy and form covalent bonds with one another. This linkage distorts the double-helix of the DNA, blocking transcription and translation. When repaired by photolysases, incorrect nucleotides can be inserted.

Water: Water can react with the bond between purines and the deoxyribose backbone of DNA, hydrolysing the bond and causing the purine base to seperate. A repair system, called the apurinic repair system, can repair this damage, but the DNA may be transcribed or replicated before this repair can take place, causing an adenine to be base-paired with the apurinic site.