What process is employed to precipitate DNA during extraction?

Precipitating DNA during extraction is primarily achieved through the addition of ethanol. When ethanol is mixed with a solution containing DNA, it reduces the solubility of the DNA, causing it to precipitate out of the solution. This is because DNA is more soluble in water than in alcohol. By carefully adding cold ethanol to a mixture that contains nucleic acids, the DNA strands clump together and become visible as a white precipitate, which can then be collected through centrifugation.

While the addition of salt can facilitate the precipitation process by helping to neutralize the negative charges on the DNA backbone, it is the presence of ethanol that is critical for the actual precipitation to occur. Heat treatment and centrifugation are important in the overall process of extracting DNA, but they do not specifically lead to precipitation. Heat can denature proteins, and centrifugation helps separate different components, but without the addition of ethanol, DNA would not precipitate efficiently. Therefore, ethanol is the key component in the precipitation step of DNA extraction.