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The human genome is comprised of sequences of three billion DNA nucleic acids. Analysis of DNA sequencing has improved our understanding of many molecular processes relevant for normal physiology and disease. Genetic alterations are the basis of cancer development and can be divided into germline and somatic mutations. While germline mutations are hereditary, somatic mutations are acquired throughout life as a consequence of DNA replication errors, or from some environmental insult such as smoking, occupational or environmental carcinogen exposures, and ultra-violet irradiation. Analysis of the genomic sequence of tumours can identify mutation signatures specific for some environmental factors and direct guidelines for recommended exposure limits and cancer prevention.