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A somatic mutation is any alteration at the cellular level in somatic tissues that occurs 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 germline mosaicism, affecting organismal development. The effects of mosaicism on overall health depend on the specific gene affected by the mutation. Environmental stressors and errors that occur during cellular replication increase the risk of somatic mutations.[1] Radiation, exposure to certain chemical compounds, and intracellular processes that generate free radicals are stressors that can cause cellular damage and DNA mutations. After a mutation occurs, the newly altered DNA undergoes normal cellular replication and then becomes incorporated into all subsequent progeny 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 confer a growth advantage and promote tumor survival.[2] Mutations that alter the machinery of DNA replication or repair arrest the cell cycle, leading to 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.[3]