Does your food contain GMO DNA?
DNA Extraction
1. Place approximately 1-2 mm3 of your food sample to a clean 1.5 ml tube.
2. Macerate tissue using a blue pestle and hand homogenizer for 30-60 seconds. You will still have some
solid pieces, but you should have a slurry. If your tissue is very dry such as tortilla, you may need to add 50
µL of extraction buffer to aide in homogenization.
3. Add 400 µL (or 350 µL if you have already added 50 µL) of extraction buffer (200mM Tris HCL at pH
7.5, 250 mM NaCl, 25 mM EDTA, 0.5% SDS).
4. Vortex for 5 seconds.
5. Centrifuge the extract at 13,000 rpm for 3 minute.
6. While centrifuging, add 300µL of isopropyl alcohol to a fresh Eppendorf tube.
7. Add 300µL of the supernatant into the isopropyl alcohol tube, take care to not bring any solid material,
you may need to add less than 300µL.
8. Leave the mixture at room temperature for 2 minutes.
9. Centrifuge at 13,000 rpm for 5 minutes.
10. Quickly pour off the liquid, making sure not to dislodge the pellet.
11. Close tube, centrifuge for 10 sec.
12. Remove remaining liquid with eppendorf pipet.
13. Add 1 mL of 70%-75% ethanol to the Eppendorf tube.
14. Centrifuge at 13,000 rpm for 2 minutes.
15. Quickly pour off the ethanol making sure not to dislodge the pellet.
16. Close tube, centrifuge for 10 sec.
18. Remove remaining liquid with eppendorf pipet, and leave the Eppendorf tube open for 15-20 minutes at
37°C. Your sample should be dry and should not smell of ethanol.
18. Add 100µL sterile water to the Eppendorf tube to dissolve the pellet. You may need to pipette the liquid
up and down vigourously several times to resuspend the pellet. It is highly likely that much of the pellet will
not dissolve. If everything dissolved then the DNA should be dissolved in this water and can now be used
for PCR amplification. Be sure your tube is labeled. If the pellet is not completely dissolved, proceed to #19.
19. If there is material theat did not dissolve, then centrifuge at 13,000 rpm for 3 minutes to pellet the debris
that did not dissolve in water and pipette the liquid into a clean sterile tube. The DNA should be dissolved in
this water and can now be used for PCR amplification. Be sure your tube is labeled.
PCR Procedure
1. Mix each of the following into a PCR tube:
a. 10 µL of GoTaq
b. 4.5 µL of each of two primers (forward and reverse)
c. 1 µL DNA extract
2. Mix the mixture by tapping on the PCR tube. Your total volume will be 20 µL.
3. Centrifuge briefly to pool the PCR ingredients if necessary.
4. Place the prepared PCR tube into the PCR machine and run using the following sequence:
a. Heat to 95º C for 5 minutes
b. Cool to 95º C for 30 seconds
c. Cool to 57º C for 45 seconds
d. Warm to 72º C for 30 seconds
e. Repeat this sequence 35 times beginning at step b
f. Hold at 72º C for 7 minutes before taking to 4º C for storage
g. Samples are now ready for gel electrophoresis
Gel Electrophoresis
1. Load 10 µL of molecular weight marker into one of the electrophoresis gel wells.
2. Load 10 µL of the sample into another well of the electrophoresis gel.
3. Repeat step 2 (using sequential empty wells) until all PCR samples have been loaded into the gel.
4. Run the electrophoresis between 100 and 125 V.
5. Stain gel with Ethidium Bromide.
PCR worksheet
Reagent name
One
Check if
reaction
added
(µL)
GoTaq
10
F-primer
4.5
R-primer
4.5
DNA extract
1
Total volume
20
2X GoTaq (contains Taq polymerase, dNTPs, MgCl2, and buffer for ideal reaction and loading dye for
electrophoresis)
Project Name: _____________________________ Researcher initials:______ Date:____
Samples loaded in gel:
well
1
sample
2
3
4
5
6
7
8