DNA is the recipe for life; within its billions of codes lay the groundwork for organisms. The study and analysis of DNA--in everything from genealogy to criminal investigations--has become very common. To examine DNA, though, it must first be extracted from a sample. Whether it is a lock of hair or a bit of blood, DNA can be found in nearly everything that makes up an organism and its extraction procedures have been perfected over the decades.
Cell Lysis
Lysis is the action by which cells are literally broken, causing their contents to spill out for analysis. The cells that contain the DNA sample to be extracted must be opened, thus allowing us to gain access to the lysate, or the fluid inside. This is achieved by several methods, the most common of which is sonicating. Sonicating is the process by which condensed sound is applied to the cells, thus agitating them and breaking their intermolecular reactions. Other methods to induce lysis include introducing a virus, which breaks it open from the inside; enzymes which eat away at its surface; and osmosis, which involves placing the cells in water, allowing the fluid inside of them to make its away to the outside, where it can be extracted.
Membrane Removal
Next, the lipids around the cell's membrane must be removed. Lipids are types of fats, waxes, monoglycerides, phospholipids and other naturally occurring molecular substances used as structural components to cell membranes, giving them some rigidity. These are removed by washing the cells' lysate in a detergent solution, usually a form of chromic acid.
Protein Removal
After the lipids have been successfully removed from the lysate, it's now important to remove any remaining proteins. This is accomplished through the addition of what's known as a protease. A protease is a special enzyme designed to break down the given proteins. This action is called proteolysis, whereas the protease causes hydrolysis (breaking down) of the bonds that hold amino acids together. Amino acids make up proteins, and without their configuration, the protein breaks down.
Precipitating
It's finally time to view the pure DNA. This can be done by dipping the lysate into ice-cold alcohol, usually ethanol. Since DNA is insoluble in alcohol, it will clump together. When the mix is stirred with a metal spoon, the DNA will visibly wrap around the metal, resembling white cotton. This is known as precipitating, with the DNA known as DNA precipitate.
Isopropanol
Along with ethanol, isopropanol also is occasionally used do extract DNA precipitate. On the positive side, it is more efficient than ethanol, yielding a higher concentration of DNA when used. However, it is also far less volatile and requires more time to dry. It may also be noted that the DNA may not adhere as well to the spoon or tube when using isopropanol.
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