DNA sequencing autoradiograph - coloured

Di-deoxy sequencing is a way to determine the order of bases (A,C,G and T) in a piece of DNA. Using a DNA polymerase, a new strand of DNA is made from the existing strand in a test tube. By incorporating a radioactive label and a mixture of bases, some of which stop the new chain when they are randomly inserted, many new strands of different lengths are generated. These can be separated by electrophoresis on an acrylamide gel and the sequence of bases worked out.