Why is isopropyl alcohol used in dna extraction

Be careful not to overdry the sample, since this can denature the DNA; just leave the washed pellet on the lab table for a few minutes. If isopropanol has been used during the extraction instead of ethanol, the sample may not adhere as tightly to the tube and may require a longer drying time.

Incubate on ice for 15 minutes. In case of small DNA fragments or high dilutions overnight incubation gives best results. Discard supernatant by decanting or pipetting, being careful not to throw out DNA pellet which may or may not be visible. Add 0. Calculate after addition of sodium acetate.

Room temperature isopropanol minimizes coprecipitation of salt. Discard supernatant by decanting, being careful not to throw out DNA pellet which may or may not be visible.

Isopropanol precipitated pellets are often difficult to see and loosely attached. Mark outside of tube before centrifugation for easy identification. Ethanol also makes the DNA less soluble for another reason.

Since the ethanol molecules can form interactions called hydrogen bonds with water molecules, they decrease the number of water molecules available to hydrate the DNA. Between this effect and the lower dielectric constant, the ethanol basically causes the DNA to aggregate with positive ions in the solution, forming a solid or precipitate at the bottom of the tube.

Precipitating the DNA serves to make it more concentrated because other contaminants in the solution are not precipitated at the same time. The ethanol wash also serves to remove low molecular weight contaminants like salts and detergents. Ethanol can also be used to precipitate RNA for much the same reasons, although precipitation of RNA will typically require more ethanol. Based in San Diego, John Brennan has been writing about science and the environment since Components of Lysis Buffers.

Because DNA is less soluble in isopropanol, isopropanol allows precipitation of larger species and lower concentrations of nucleic acids than ethanol, especially if you incubate at low temperatures for long periods of time. So now you know the difference between ethanol and isopropanol precipitation, and when to use each method.

Good luck with your DNA precipitations! Has this helped you? Then please share with your network. Hi in my script it is nowhere mentioned that we are supposed to use salt.

Does it still work without adding salt or is it a mistake in the script? Could you please help me out? Thanks for this clear explanation.

It helps a lot the students who discover the beautiful world of molecular biology! Facebook Twitter LinkedIn More.