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DNA sequencing. Gloved hand holding a petri dish containing banded DNA sequences or genetic fingerprints. The pattern of bands represents the chemical sequence that forms the genetic code for a section of DNA (deoxyribonucleic acid). The DNA sample was cut into fragments by an enzyme. These fragments were then placed into a gel in the petri dish and separated by electrophoresis, the application of an electric charge. DNA sequencing is used in forensic science, medical research and genealogy. (KEYSTONE/SCIENCE PHOTO LIBRARY/TEK IMAGE)