How to extract your own DNA

[Insertnamehere]

http://www.popsci.com/how-to-extract-you...lt&src=syn

Yeah? And then what?

Insertnamehere come to the rescue!

This is a basic protocol for genomic DNA extraction and visualization. Basic as it is, it's nearly useless for serious purposes.

First thing to have in mind is location: as we all (should) know eukaryote DNA is compartimentalized in the nucleus. That means we need to get through 2 lipidic membranes to get it out of the cell.

Simple enough to disassemble the membranes and thus burst any cell the fuck open: any detergent.

Laboratory grade detergents could be SDS, Triton X-100.

Home detergents do the trick, but, in serious downstream applications, picking a proper detergent is crucial because it can interfer with reactions, analysis, etc.

Next thing is to immediately inactivate DNAases which would otherwise enzymatically degrade DNA rapidly.

In this home experiment, pineapple juice is added. If you, like me, can't eat pineapple without bursting into blisters, then you'll know about bromelain. It's a protease enzyme. That is, a protein dedicated to degrade other proteins. So, now our nucleases are gone.

In the lab, you use a simple chelating agent, EDTA to "kidnap" Calcium and Magnesium, which are needed co-factors without which nucleases (DNAase, RNAase) can't function.

Then we need to separate DNA from the rest of the macromolecules and cellular debris. To this end, you add salt.

DNA is, at physiological pH, a heavily charged molecule (negatively charged) due to the phosphate groups of its polymeric "skeleton" which makes it extremely water-soluble. But add salt, and it will compete with the DNA for the sorrounding water molecules.

DNA, being a large ass molecule, can't really compete with small salt ions. It will being to clump together.

Finally, the last nail in the coffin, (nearly) absolute cold Ethanol poured gently so it doesn't mix with the solution. Being extremely water soluble, DNA is almost insoluble in organic solvents, even polar ones like alcohols.

The multifacetic proteins, the highly hydroxylated carbohydrates and the happy-in-detergents lipids all have a nice environment around them and they will feel quite content staying in it.

DNA however, won't like being in a highly ionic solution competing with it and won't like ethanol, in which it can't be dissolved, either. So, it will remain at the interfase bewteen these 2 liquids, from which you can pick it up.


In any serious case, you would need additional purification steps for any kind of downstream application. For one, resuspension in water and addition of RNAase is due, to eliminate RNA which will interfere with pretty much anything you want to do with DNA. Afterwards, silica columns can be used to retain the DNA while washing away everything else, you can elute the clean DNA with water (not just any water of course: ultra pure, nuclease free, DNA/RNA free water...nothing you can purcharse in the store, that's for sure). Or solvent change can be performed with cold absolute ethanol to precipitate the DNA, etc.

The purity of the DNA is very important for any further use in inverstigation.

Here is a paper with a protocol as used in a lab

http://www.funpecrp.com.br/gmr/year2011/...mr1055.pdf