After precipitating DNA, if washing processed with water instead of 70% ethanol, then one will be able to recovered DNA immediately or it will get away with water.
Do the DNA will get completely dissolved immediately after adding water and the solubilization continues during immediate centrifugation?
How much time water takes to dissolve DNA?
The ethanol wash is primarily to get rid of excess salts, which are soluble in 70% ethanol, but DNA is not. Washing in water instead will simply dissolve both, so as Kenneth says, the ethanol is a key step
If you have reasonable quantity of DNA not worried about loosing some, it should be OK to wash the precipitated DNA with sterile water. This eliminates the salts used for precipitation, however, you need to wash gently with out mixing it water. Only gentle rinse.
70% Ethanol removes salts fro the DNA pellet and at the same time remove some water molecules from DNA. Removal of water molecules make the DNA less hydrophilic, which is why its difficult to dissolve. If you wash your freshly isolated DNA pellet in water you run the risk of dissolving most of your DNA in the solution along with the salt since DNA will be very soluble. But still as Witwer said you can recover the dissolved DNA by precipitating.
As Kenneth and Rob said 70% ethanol washes are crucial steps in DNA precipitation. A wash in pure water will simply resuspend the DNA pellet without removing any residual salts.
Before use 70% ethanol solution for DNA washing, precipitate DNA by pure isopropanol, its better way.
Govind, the principles behind nucleic acids precipitation are readily available online by simple googling. DNA is a polymer with extensive phosphate moieties and many potential H-bond forming moietes on the N-bases as well as the pentose. This makes DNA *HIGHLY* water-soluble (not compared to NaCl, but compared to most polymers). So, what will happen if you wash it with water? Almost the same thing as washing a pinch of sugar with water.
Solubility of a material (DNA here) in water depends to a great deal on the material's potential to form H-bonds with the water molecules. Now, if you add a small molecular weight polar/hydrophilic component to the aq. solution of the material in excess, then the great majority of water molecules are captured by the excess of the hydrophilic component (ethanol here), leaving hardly any free water molecule to H-bond with the material (DNA). This leads to clumping of the material (DNA) together, called precipitation. This process is facilitated by inclusion of salts like NaCl, KCl, LiAc, NH4Ac etc, which (i) further reduce the availability of water molecules for the material (DNA), and (ii) cause cation-mediated condensation of DNA. Effective dissolution of the DNA post-precipitation, thus, will need that the salt is removed as much as possible. Now, washing the precipitated material with the same concentration of the hydrophilic excess component (ethanol) sans any salt will effectively remove the majority of the salt, while retaining the DNA precipitated. The precipitate is then simply dried and dissolved in a mildly alkaline buffer (usually TrisCl pH 8.0; with a little EDTA to keep divalent cations and nucleases quiet), since DNA is acidic.
Water will help in solubilizing DNA and thus you will lose the isolated DNA . Why would one like to wash with water in the first place after isolating good DNA?
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