Question

How can DNA be extracted from saliva?

Answer 1

it is quite a tricky one to do.

Explanation:

there is a traditional protocol too proteinase K-saline precipitation protocol
a video for same is
http://www.jove.com/video/246/isolation-of-genomic-dna-from-mouse-tails
where replacing the mouse tail with saliva will get the job done.

1. collect saliva from an individual.

2. add 720`mu`l STE and 30`mu`l Proteinase K

3. incubate at 55°C for 3 hours
4. inactivate proteinase K by keeping at 70°C for 5 minutes.
5. put it on ice for about 5 minutes.
6. centrifuge it for 10 minutes at 13,000rpm
7. take supernatant and mix with 720`mu`l isopropanol
8. centrifuge for 5 minutes at 13,000 rpm
9. wash the pellet with 70% ethanol. vortex briefly
10. spin the pellet containing genomic DNA for 5 minutes.
11. dry the pellet and add 100`mu`l of Tris-EDTA (TE) to dissolve the pellet.

I must mention most of the isolation are carried out using a kit. to give a flavor of the same it is given below

there are lot of papers available on commercial method to do so. one of it is Oragene kit combined with prepIT•L2Pextraction kit which proposes that it can isolate up to 110`mu`g of genomic DNA with very less amount of sample requirement.

details of protocols are given below

1. collect saliva from an individual.

2. keep it in Oragene kit (require liquid saliva and no bubbles)

3. mix the sample with gentle inversion till it mixes
4. put it at 50°C for about 1 hour. (can keep for overnight too)
5. take 550`mu`l of sample and add 20`u`l of prepIT•L2P buffer
6. vortex it and put it on ice for 10 minutes.
7. centrifuge at room temperature for 5 minutes at 15,000xg

8. collect the supernatant

9. add 600`mu`l 95% ethanol and mix the solution. let it stand for 10 minutes at room temperature

10. centrifuge at room temperature for 5 minutes at 15,000xg
11. discard the supernatant add 75% ethanol to the pellet and let it stand at room temperature.
12. remove the ethanol and without disturbing the pellet
13. add Tris-EDTA buffer (TE in short) and vortex to dissolve the pellete.

complete protocol is available here link for the protocol is given bellow:
http://www.dnagenotek.com/US/pdf/PD-PR-006.pdf