DNA Precipitation Intro

   DNA, the molecule of life, carries the genetic information from generation to generation. Deoxyribonucleic acid, found in all living organisms, is a double helix containing millions of pairs of nucleotide bases, each base being connected to a deoxyribose sugar and a phosphate group. The four bases are adenine, guanine, thymine, and cytosine; adenine pairs with thymine and thymine pairs with guanine. In short, DNA makes us who we are. It determines everything from eye color to skin color to body type to susceptibility to certain diseases. Certain sequences of DNA that code for a specific trait are called genes. Differences in the base pairs in genes, often occurring because of mutation, are what account for diversity among organisms.
   In humans, DNA is stored in the nucleus of all cells. Every cell has a complete set of DNA, but only certain genes are expressed in each cell. What DNA (genes) really does is code for certain proteins in the cell. DNA is first transcribed into messenger RNA, and this mRNA travels out of the nucleus to the ribosomes where the genetic message is read and the correct proteins are built.
   In this lab we will attempt to precipitate DNA out of solution, extract it, and put in in a necklace. Visualizing the genetic molecule in this way could be very beneficial to scientist's in the real world. Isolating DNA allows biologists to study and compare between individuals or different species. The sequencing of DNA has been an extremely important development of the last twenty years and will have even more significant benefits in the future when we are more knowledgeable.
   The precipitation of DNA is actually a very simple process. First, we will chew on the insides of our cheeks to loosen the cells. Then we will swish a saline solution around in our mouths to extract the cheek cells. The isotonic solution has a concentration that is favorable to the cells. In order to get to the DNA we will add a lysis buffer that breaks open the cell membrane by dissolving the phospholipids. To further isolate the DNA, we will break down the histone proteins DNA is wrapped with using an enzyme called protease. Protease will also destroy the DNAse in the cytoplasm that would otherwise dismantle our DNA. We will speed this reaction up by placing the test tubes in a hot water bath. If our DNA was in just a water solution the DNA, which is negatively charged and polar, would interact with the polar H2O molecules. The added salt binds with the DNA, making it non-polar. We complete the lab by adding cold ethanol, which has a lower freezing point than water. This allows us to get the solution to extremely low temperatures, stimulating precipitation.
   Finally, we will have a beautiful necklace containing the very molecules that give us life and make us who we are.