Genetics, Somatic Mutation

Excerpt

A somatic mutation describes any alteration at the cellular level in somatic tissues occurring after fertilization. These mutations do not involve the germline and consequently do not pass on to offspring. Somatic mutations are a normal part of aging and occur throughout an organism’s life cycle either spontaneously as a result of errors in DNA repair mechanisms or a direct response to stress. Mutations occurring early in development can cause mosaicism within the gene line, impacting organism development. The impacts of mosaicism on overall health due to mutations depend on the specific gene the mutation affects.

Environmental stressors and errors that occur during cellular replication increase the risk for somatic mutations to occur. Radiation, exposure to certain chemical compounds, and intracellular processes generating free radicals are stressors placed on the cell that can cause cellular damage and mutations within DNA. After a mutation occurs, the newly altered DNA undergoes normal cellular replication and then becomes incorporated into all subsequent prodigy cell lines within the individual.

Somatic mutations have received the most study in human carcinogenesis. Various mutations in oncogenes, tumor suppressor genes, and DNA repair mechanisms can select for increased growth advantage and tumor survival. Mutations that alter the machinery for DNA replication or repair arrest the cell cycle causing cell death. As a result of defects in tumor suppressor genes, oncogenes, and genes required for genome stability, the individual inherits an increased risk for cancer in corresponding genes as somatic mutations continue to accumulate within already unstable genes.