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DNA Extraction from … The Tools of Molecular Biology – Scientists use their knowledge of the structure of DNA and its chemical properties to study and change DNA molecules. Copyright Pearson Prentice Hall The Tools of Molecular Biology – Scientists use different techniques to: • extract DNA from cells • cut DNA into smaller pieces • identify the sequence of bases in a DNA molecule • make unlimited copies of DNA Copyright Pearson Is DNA in My Food??? • DNA is present in the cells of all living organisms. • The process of extracting DNA from a cell is the first step for many laboratory procedures in biotechnology. • The scientist must be able to separate DNA from the unwanted substances of the cell gently enough so that the DNA does not denature (break up). The Tools of Molecular Biology • In genetic engineering, biologists make changes in the DNA code of a living organism. Copyright Pearson Prentice Hall DNA Facts • Each cell contains 9 feet of DNA • In an average meal, you EAT approximately 55,000,000 cells • This is equal to approximately 93,205 miles of DNA DNA • DNA is found in the nucleus of all eukaryotic cells • Most cells have the diploid 2n chromosome number • Many plants are polyploid (contain several sets of chromosomes) • Strawberries are octaploid 8n DNA • DNA is enclosed in a nuclear and a cell membrane made of phospholipids • DNA is also coiled around proteins • Both the phospholipid layer and the proteins must be removed to see DNA NUCLEUS with DNA To Extract DNA, You Must Remove … • • • • Cell membrane Cytoplasm Nuclear membrane Proteins How Do I Begin? • 1. Place the strawberry in a zip lock bag and remove the air • 2. Squash the berry with your hand to begin the process • 3.Add the soap solution to help dissolve the cells membranes and nuclear membranes. • 4.Mix together in the ziploc baggie well. Try not to make lots of bubbles. • 5.Set up test tube with funnel on top and filter in funnel • 6.Pour strawberry and soap solution into filter and let it drain into the test tube • 7. Test tube should fill up to about 1/4 to 1/3 of the lysate solution • 8. Hold the test tube at a 45 degree angle in one hand. Slowly add 3-5 ml of ice cold ethanol down one side of the test tube to form a layer over the strawberry solution • 9. Wait 2-3 minutes for the alcohol to precipitate the DNA out of the solution. Cell Membrane • Cell membranes are made of phospholipids • Phospholipids won’t dissolve in water • What do you use in your home to remove oils from your hands or your dishes? • SOAP or DETERGENT! Soap & Detergent • Soap gathers between oil and water capturing the oil in a bubble called a micelle • When you wash your hands, the soap carries the oils away • Dawn dishwashing works BEST to remove phospholipid membranes Soap & Detergent • By adding a small amount of table salt (NaCl) to the soap solution, the solution can punch holes in the nuclear and cell membranes • The soapy solution also helps removes proteins Another Way to Remove Proteins • DNA is tightly coiled around proteins called histones • Proteins must be removed to see DNA • Enzymes, like the ones found in meat tenderizer, can remove protein Extracting the DNA • The contents of the cell (organelles, proteins, etc.) must be separated from the DNA • The larger cell parts can be removed by filtering the solid from the liquid Extracting DNA • To see DNA, it must be extracted or “spooled” from the remaining liquid you filtered • DNA dissolves in water, but NOT in alcohol • Adding COLD ALCOHOL will cause DNA to precipitate (separate out) from the liquid filtrate Collecting the DNA • The DNA will appear as a white precipitate once the alcohol is added • HOLD THE TUBE by the TOP, not the bottom so the DNA strands won’t fragment from the heat of your hands! Spooling the DNA • DNA is sticky and will adhere to other surfaces • A glass stirring rod can be used to spool (remove) the DNA by using a turning motion