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DNA extraction - details about ethanol precipitation - (Sep/06/2005 )

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Can DNA be isolated without ethanol precipitation?

-amty-

QUOTE (amty @ Sep 6 2005, 09:27 PM)
Can DNA be isolated without ethanol precipitation?

Yes.
E.g. with the Promega mini wizard kit.

-Theo22-

Thanks!
Can you tell me the principle behind DNA precipitation using ethanol?
I think ethanol does not selectively precipitate DNA
so the degree of contamination with salt (used in buffer) is really high ,
How can this be avoided?

-amty-

You need high salt (eg NaOAc) to precipitate the DNA using ethanol. After precipitating, use a 70% ETOH wash to remove the salts.

-tap14-

Does DNA precipitation with Isopropanol requires the salt as well?

-haohao-

Isopropanol uses lower salt concentration.
http://www1.qiagen.com/literature/qiagenne...399/993prah.pdf

-tap14-

what is the purpose for using phenol -chloroform in DNA extraction?

-amty-

Phenol/chloroform is used to purify the DNA (removing proteins, inactivating DNAses etc). The isoamylalcohol in the phenol/chloroforn is used for better seperation between phenol-layer and water layer (containing the DNA). The second chloroform step will remove all remaining phenol from your water phase.

-Theo22-

Iam extracting DNA from mosquitoes,
how much sample should I use?(currently using 10nos/ml)
I have followed ethanol precipitation
but I could not see the white thread
of DNA on adding ethanol.

-amty-

You need to have a high concentration of DNA to see it precipitate in solution. I assume you are performing some form of a lysis step prior to all this?

-tap14-

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