Caption

DNA fingerprints. Banding patterns on DNA sequenc- ing autoradiograms forming "genetic fingerprints" which enables genes to be mapped. The pattern of black bands gives the sequence of base pairs that form the genetic code for a section of DNA. A sample of DNA has been cut into fragments by an enzyme and marked with a radioactive tag for sequencing. The DNA fragments are then separated by electrophoresis in an agarose gel, moving different distances along the gel according to their size. The result is this banding pattern which is unique to each person. DNA fingerprints can be used to prove whether people are related, and can help to identify and convict criminals.