why alcohol instead of water?
during DNA purification we do we use alcohol.
would you please explain me the steps in which we can get purified DNA.
+details.
thanks alot 
have a nice day
the website says:
Precipitate DNA (salt + alcohol) : For routine precipitation of nucleic acids, you need enough salt to
neutralize the repulsion among the negatively charged strands of DNA, and
enough alcohol to pull water molecules out of the DNA strand.
can you expalin how?
when we lysis enzyme to break down membrane and hen precepitate protien and centrigue them. then we get rid of them.
after that we r left with the crude lysate , and now that it contains the DNA that is (-) charged, the strads will repullse each other. that is why we ADD THE SALT TO REACT with + charges. but then when we extract DNA it will have attached + charged molecules.
+ one more thing: where does the water comes from?? the one that we want to remove using alcohol?
I KNOW IT IS TO MUCH BUT I REALLY NEED TO KNOW WHY : }
THANKS in advance
One Response
Altmer
02 Feb 2010
The concept is basically that that DNA is insoluble in alcohol causing it to precipatate from solution. So when it is centrifuged it aggregates together (this is why you must negate the negatively charged DNA with salt) and forms a pellet at the bottom of the centrifuge tube.
Most of the water you add yourself, you need the DNA in solution as it is far too delicate and in such a minute quantity that it can;t be handled any other way. Plus there are already water molecules from the cell cytoplasm associated with the DNA.