Question

im the DNA extraction from a banana procedure it states: "Try to prevent the alcohol from mixing with the banana mixture." Subsequent steps also emphasize that you should "avoid any sudden disturbance"

Why is this important? Consider what is present in the test tube and whag the purpose of these steps is.

why is it important to keep the alcohol and banana mixture from mixing?

Answer 1

During DNA extraction from any biological material, we normally use 70% alcohol/isopropanol for precipitation of DNA. Once the cell is bursted by using detergent solution (CTAB) or hyperosmotic solution (8-10M NaCl) then the contents will come out of the cell. This mixture will contain all macromolecules including proteins, lipids, carbohydrates, nucelic acids (DNA/RNA), metalic ions etc. and after we centrifue the tube the DNA remains in the supernantant and inorder to precipetate DNA, alcohol (Ethanol/isopropalol) is added in the supernatant layer which later precipitates DNA as cloudy material and any disturbance can lead mixing of DNA with other cellular components.

Therefore, inorder to have pure DNA without contamination of other cellular components like proteins, it is always advisable not to allow mixing of alcohol layer with the other banana mixture.