What is DNA fingerprinting? Describe the steps of the technique and give two applications.

1. 1 · Define it. A technique to identify a person by the pattern of differences in repetitive DNA.
2. 2 · Give the basis. Satellite DNA, especially VNTRs, is highly polymorphic, inherited, and the same in every tissue of a person.
3. 3 · List the steps.
   • Isolation of DNA
   • Digestion by restriction endonucleases
   • Separation by gel electrophoresis
   • Blotting onto nitrocellulose or nylon
   • Hybridisation with labelled VNTR probe
   • Detection by autoradiography
4. 4 · Draw the result. [Diagram: lanes for mother, child and two men, with matching bands at the same height]
5. 5 · Give the applications. Forensic science, paternity testing, population and genetic diversity studies.
6. 6 · Link to real life. DNA tests help police solve crimes and families settle paternity disputes.
7. 7 · Close in one line. So, except for identical twins, no two people share the same DNA fingerprint.

Scoring tip: Write the six steps in the right order with the key word for each. Order matters for full marks.