1. Gel Electrophoresis
Ms. Cuthrell

2. 3.3.1
Interpret how DNA is used for comparison and identification of organisms.

3. Gel Electrophoresis
A technique used to separate molecules based on size.
Look at the name to remember the requirements: gel and electricity.

4. DNA Fingerprint
The result of gel electrophoresis is a DNA fingerprint.
We call it a fingerprint because your DNA identifies you, just like your fingerprints.
Gel is stained using ethidium bromide which binds to DNA it shows up as bands in UV light
Draw attention to the fact that small mols are at the bottom of the gel and large ones stay nearest to the wells

5. Why electricity works?

6. Steps Involved in Gel Electrophoresis
1. Make the gel.

8. Buffer solution added to the tank
This ensures that the electric current goes through the whole tank and that maintains that ions can move in the solution

9. 2. Use restriction enzymes to cut DNA into different sized fragements.
Square tray
2-3 cm of agarose gel which is left to set, can also be made of starch or polyacrylamide, special comb put in so that there are small wells left in the gel

10. Dye added to the DNA
Makes the sample visible when it is put into the agarose wells

11. 3. Load the DNA fragments into the gel.
A bit like electronic chromatography
The fragments are seperated according to size in process called gel electrophoresis

12. Glycerol also in the loading dye

13. 4. Apply the electric current to the chamber and wait.
Safety cover is put over the top and the current is switched on
The dye will migrate through the gel toward the positive electrode, as will the DNA
Depending on how much voltage is applied and how warm the gel is and size and shape of molecules will depend on how fast the mols move through the gel
Smaller fragments will move easier so they will be closer to the positive electrode
Once the dye has moved through the gel to the buffer, the electrical current is switched off and gel is removed from the tray

14. DNA Fingerprint
Shorter fragments move faster than longer fragments so they are found at the bottom.

16. Applications of DNA Fingerprinting
Crime scene investigations
Paternity testing
Identifying/cataloging species (including extinct) to determine relationships or similarities