Editing DNA extraction (section)

== Basic procedure ==
* Cells that are to be studied need to be collected.
* Breaking the [[cell membrane]]s open exposes the DNA along with the cytoplasm within ([[Lysis|cell lysis]]).
** Lipids from the cell membrane and the nucleus are broken down with  [[detergent]]s and [[surfactant]]s.
** Breaking down [[protein]]s by adding a [[protease]] (optional).
** Breaking down [[RNA]] by adding an [[RNase]] (optional).
* The solution is treated with a concentrated salt solution (saline) to make debris such as broken proteins, lipids, and RNA clump together.
* [[Centrifugation]] of the solution, which separates the clumped cellular debris from the DNA.
* DNA purification from detergents, proteins, salts, and reagents is used during the cell lysis step. The most commonly used procedures are:
**[[Ethanol precipitation]] usually by ice-cold [[ethanol]] or [[isopropanol]]. Since DNA is insoluble in these alcohols, it will aggregate together, giving a ''pellet'' upon [[centrifugation]]. Precipitation of DNA is improved by increasing ionic strength, usually by adding [[sodium acetate]].
** [[Phenol–chloroform extraction]] in which [[phenol]] [[Denaturation (biochemistry)|denatures]] proteins in the sample. After centrifugation of the sample, denatured proteins stay in the organic phase while the aqueous phase containing [[nucleic acid]] is mixed with [[chloroform]] to remove phenol residues from the solution.
** [[Minicolumn purification]] relies on the fact that the [[nucleic acid]]s may bind ([[adsorption]]) to the solid phase (silica or other) depending on the [[pH]] and the salt concentration of the buffer.

Cellular and [[histone]] proteins bound to the DNA can be removed either by adding a [[protease]] or having precipitated the proteins with [[sodium acetate|sodium]] or [[ammonium acetate]] or [[phenol-chloroform extraction|extracted them with a phenol-chloroform]] mixture before the DNA precipitation.

After isolation, the DNA is dissolved in a slightly alkaline buffer, usually in a [[TE buffer]], or in [[Ultrapure water|ultra-pure water]].