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
1000 mL bekaer glass.
Hot plate with bath
Dishwashing soap or shampoo
Table salt, either iodized or not iodized
Blender and knife to cut onion.
Timer or clock
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