ABSTRACT
Mutagenesis can occur as a result of interaction between mutagenic agents (mutagens) and genetic materials present in organisms. Although spontaneous mutations and natural selection are the major means of evolution, in recent decades, a number of toxicants have been found to induce mutagenic effects in a variety of organisms. Mutations can be produced by external factors (e.g., high temperatures), toxic chemicals (most carcinogens, etc.), radiation (ionizing and nonionizing), as well as internal factors (e.g., cellular metabolism and respiration, reactive oxygen species, and reactive nitrogen species), and DNA replication/transcription error. Electromagnetic fields and free radicals generated from electronic equipment/devices, medical devices (e.g., x-ray, MRI, etc.), electricity, microwaves, radar, and cellular phones could be sources of mutations. Mutations are classified into microlesions (e.g., gene mutation: frame shift and base substitution) and macro lesions (e.g., chromosomal abnormalities: gap, fragments, deletion, ring, translocation, and numerical change). Some individuals exhibit mutations in skin cells or other tissues, termed somatic mutations. In contrast, germ mutations occur only in the sex cells and are more threatening because they are transmitted to subsequent generations.
