DNA Fingerprinting

1. DNA Fingerprinting Lauren Crews, Michael Collette, AJ Vallieres, Bryce Lescarbo

2. Process of DNA Fingerprinting: Step 1 The first step it to pour the restriction enzymes in to the DNA. • These enzymes work like scissors, cutting the long DNA molecules at different locations. • Where the DNA gets cut depends on the code within the DNA molecule and the code within the enzymes. • The length of those fragments will vary from person to person because the code fore very persons DNA is different.

3. Process of DNA Fingerprinting: Step 2 The second step is to pour the “Agarose Gel” into the electrophoresis tray. • The Agarose Gel is a thick, porous, jelly-like substance. • It will act as a molecule strainer. • This means it will allow smaller pieces of DNA to move through more easily than larger pieces.

4. Process of DNA Fingerprinting: Step 3 The third step is to pour the DNA into a hole in the Agarose Gel. • By pouring the DNA into the hole in the Agarose Gel, the DNA fragments now lie within the gel. • The Gel is now ready for step 4.

5. Process of DNA Fingerprinting: Step 4 The fourth step is to turn on the electrophoresis tray and begin electrophoresis. • Electrophoresis is the process of moving molecules with an electric current. • The DNA fragments have a slight negative charge, so they move toward the trays positive end. • Since the gel acts like a strainer, the smaller DNA moves through the gel more easily and thus moves farther than the larger ones.

6. Process of DNA Fingerprinting: Step 5 The fifth step is to place the nylon membrane on top of the gel. • Since the Agarose Gel is difficult to work with, the DNA is transferred to the nylon membrane. • This membrane looks like a sheet of paper. • The DNA gets sucked into the membrane as liquid travels up from the gel toward the absorbent nylon.

7. Process of DNA Fingerprinting: Step 6 The sixth step is to add the probes to the nylon membrane. • These probes are pieces of DNA that have been radioactively labeled. • These probes attach themselves to the DNA fragments of the nylon membrane. • They attach only where their code encounters a certain sequence of code among the various DNA fragments. • All of the excess probes that don’t attach to the DNA get washed away.

8. Process of DNA Fingerprinting: Step 7 The seventh step is to place a sheet of x-ray film on top of the nylon membrane. • The radioactivity from the probes, which are now present at only a few locations on the nylon membrane, exposes corresponding areas on the x-ray film.

9. Process of DNA Fingerprinting: Step 8 The eight and last step, is to put the x-ray film in a developer. • The film displays the locations on the nylon membrane where the probes attached themselves to the DNA fragments. This is your DNA Fingerprint

11. How conclusive is the evidence of DNA Fingerprinting? • DNA Fingerprinting is almost completely conclusive. • DNA can only match to one individual unless there are twins involved.

12. Where is there a possibility for error? • There is a possibility for error in anything that involves human contact. • Humans aren’t perfect and therefore, make mistakes. • So when matching a DNA Fingerprint of a suspect to the DNA Fingerprint of a bit of DNA found at the crime scene, you can mistakenly identify the wrong person.