Biotech 2nd Edition Sample Ch. 4 Biotechnology Sample Ch. 4 - Page 4

Laboratory 4b Precipitating DNA out of Solution: DNA Spooling Background DNA is arguably the most important molecule in living things. The long, thin fibers in the molecule store all of the information needed to produce all of the molecules in an organism, either directly or indirectly. The structure of a DNA molecule is related to its function, as it is with all molecules. To conduct genetic engineering, scientists need DNA in pure form. DNA must be purified out of cells or viruses, isolating it away from other molecular contaminants, such as proteins, carbohydrates, and lipids. Based on its molecular characteristics, DNA can be drawn out of cellular or aqueous solution. These characteristics include the long double-helix shape and the charged phosphate groups on the outer sugarphosphate backbone. The phosphate groups are repelled by nonpolar solutions, such as alcohol. In this experiment, DNA molecules are precipitated from solution and spooled onto a glass rod (see Figure 4.2). The starting DNA Hold the container and rod so the stock solution contains DNA that has already layers are parallel to the floor. been isolated from the nuclei of salmon sperm cells by technicians at the manufacturer. They have collected sperm samples, exploded the sperm cells, separated the contaminant proteins from the DNA, pulled the DNA out of the remaining aqueous solution using EtOH ethanol and then dried the pure DNA strands bubbles trapped to form the crystalline DNA purchased by your in DNA strands supervisor. Your supervisor has put the pure aqueous DNA into TE buffer and let it go back into DNA layer Figure 4.2.  Spooling.  Keep the glass rod almost parallel to the floor solution. Your task is to pull the pure salmon and scoop at the interface between when spooling so that Twirl it is easier to scoop and twirl DNA molecules testes DNA strands back out of solution for theletalcohol andstrands aqueous around the rod. Don’t the DNA fall(watery) off the DNA glass layer. rod. later use to provide the reagent DNA for this experiment. Purpose Can DNA be spooled out of solution? What does it look like? What yield of DNA can be recovered during the isolation? Materials Beakers, 50 mL DNA, salmon testes, 4 mg/mL Pipet, 2 mL Pipet pump, blue Micropipet, P-1000 Micropipet tips for P-1000 5M NaCl Ethanol (EtOH), 95% Glass rods Tubes, 15 mL conical Tube racks for 15-mL tubes Permanent lab marker pens Plastic beaker, 1L Tri pour® Caution: Alcohol is flammable. Keep away from flame or ignition sources. DNA Isolation and Analysis 69