Preface
In this experiment, onions are used, this is because the onion has a low starch content, which allows the DNA to be clearly visible. Salt protects the negative end of the DNA phosphate, allowing the tip to come closer so that DNA can precipitate from a cold alcohol solution. Detergents cause cell membranes to break down by dissolving lipids and proteins from cells and disrupting bonds that hold the cell membranes together. Detergents then form complexes with lipids and proteins, causing them to precipitate the solution

Equipment and materials
Ethanol 95%.
Thermometer
Plate.
Measuring cup.
1000 mL bekaer glass.
Funnel.
Filter
Test tube
Freezer
Hot plate with bath
Ice Cube.
Spoon
Dishwashing soap or shampoo
Table salt, either iodized or not iodized
Distilled water
Great onions
Blender and knife to cut onion.
Timer or clock
1. Prepare two water baths, one for temperature 55-60 ° C and another fill with ice cubes and water, about 4 ° C.2. In 250 mL beaker glass (or 1 cup), add 10 milliliters (ml) (1 tablespoon) dishwashing liquid detergent or shampoo and one 1/4 teaspoon (1.5 gram) table salt.
3. Add the distilled water to the beaker to the final volume of 100 mL. Dissolve the salt by stirring slowly to avoid foaming.
4. Cut one large onion with a knife then blender and put in 1000 ml beaker glass


8. Cooling the mixture in a water ice bath, about 4 ° C, as shown in the picture, below, for 5 minutes. In this process, press the onion DNA mixture against the side of the glass with the spoon back. This step slows DNA damage.


10. Remove the onion DNA solution into the reaction tube approximately 5 ml. Solutions can be stored in the refrigerator for about a day before use in the following steps.
11. Take a cold 95% ethanol solution from the freezer and add it to the test tube to make the ethanol layer above about 1 centimeter (cm). For best results, ethanol should be as cold as possible. Ethanol can be added to the solution
12. The DNA does not dissolve in ethanol. When ethanol is added to the mixture, all components of the mixture, except DNA, stay in the solution while the DNA settles out into the ethanol layer. The solution is allowed to stand for 2-3 minutes then white DNA will settle into the ethanol layer.

13. The formed DNA can be taken with a tooth or pipette or what stem of a crooked stirrer can take the DNA