DNA precipitation

Can anyone explain the chemistry behind salt-ethanol precipitation of DNA from solution?

Originally posted by znsho
Can anyone explain the chemistry behind salt-ethanol precipitation of DNA from solution?

The outside of DNA has electric charge which attracts the dipolar water molecules. Salt ions neutralize that electric charge by being more attracted to it than the water molecules. This reduces the attraction between the DNA and the water. Then, ethanol is added. Ethanol is less polar than water is but easily dissolves in water. Thus, the salt and the ethanol both contribute to breaking the electrostatic attraction between the DNA and the water.