DNA sequencing. Magnifying glass over the banded DNA sequences or genetic fingerprints of an autoradiogram. 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 and marked with radioactive tags. These fragments were then placed in a gel and separated by electrophoresis, the application of an electric charge. An autoradiogram of the resulting bands of radioactively-tagged DNA was made using radiographic film. DNA sequencing is used in forensic science, medical research and genealogy.