My class did a simple DNA extraction from cheek epithelial cells. The protocol involved lysing the cells with 4% detergent, 1% NaCl and vortexing, centrifuging at 11krpm to form a cell pellet, and adding cold ethanol to the supernatant to precipitate the DNA. Afterwards we were asked the following two questions but I’m not sure what the answers should be so I wanted to get other people’s thoughts.
"1. During your DNA isolation, you combined saliva, detergent and salt, vortexed then centrifuged to separate your sample into a cell pellet and supernatant. Indicate and explain where you expect the majority of the following components to be localized (i.e. the cell pellet or the supernatant).
2. What was the purpose of using COLD alcohol? Would there be a difference whether ethanol was used or butanol?"
I expected the cell pellet to contain the majority of the phospholipids, transmembrane proteins, and hydrophobic proteins, and the supernatant to contain the majority of the DNA, hydrophilic proteins and the detergent. I’m not sure why cold alcohol was used but I expect that DNA would be less soluble in butanol.