DNA extraction

Nucleic acid extraction can be divided into 3 steps, which can be optimized according to the type of sample and the downstream applications for which the nucleic acids will be used.  These steps are as follows:

1) Rupture of tissue and cell structures

2) Removal of proteins, lipids and other contaminants from nucleic acids

3) Transfer the nucleic acids to water or a buffer solution that will preserve them without interfering with subsequent work.

Solid-phase extraction methods work by causing nucleic acids to bind to solid supports, such as magnetic beads coated with silica or other materials.  The beads (or other supports) are then washed with alcohol to remove contaminants.  The support is then washed with a liquid that makes the nucleic acids soluble again, which releases the DNA from the support in a process known as elution.  A simple method is to add a solution containing a chaotrope to the crude nucleic acid extract.  Chaotropic agents are molecules that disrupt the hydrogen bonding network between water molecules.  In the presence of chaotropes, nucleic acids are previously much less soluble and bind to glass, silica-covered magnetic beads and other solid supports - allowing them to be easily separated from contaminants.  Solid-phase extraction methods may also depend on selective binding of DNA and RNA to ion exchange resins or other chemicals.