What steps are involved in removing lipids and proteins to isolate the DNA molcules??

it depends on what you are using the DNA for. You need varying degress of purity depending what you're planning on doing with you sample.

 

For example, if you just want to run DNA on a gel, you can just boil cells to break them open, and run the liquid on a gel. There are other ways to purify the sample though. Including centrifugation, precipitation and gel purification.

It also depends on the organism/tissue you want to isolate the DNA.

For PCRs the above cooking lysis is often sufficient, for blots or other things higher purity is needed.

Most protocols not using columns incorporate a phenol step to remove proteins and similar stuff.

Ok, I guess I'll answer the question:

First to remove the lipids, you have to lyse your cells with detergents (i.e. SDS at concentrations above the CMC for membrane lipids) and in some cases (bacteria) you can use alkaline lysis (NaOH).

 

To help remove proteins you can use a combination of salt salutions/alcohol solutions that will dissolve the proteins/ precipitate DNA. Also you can use a phenol step to help with this process.

 

Also you can use a column with positively charged beans to bind the DNA and elute later an alcohol elution step (this is used in alot of DNA purification kits).

 

Some ultrapure purification protocols use ultracentrifuguation to remove endotoxins

 

Centrifugution at high speeds is used in the isolation process to get rid of contaminants.

 

Hope this answers you question.

and if one wishes to isolate a particular gene from a DNA/RNA molecule then restriction enzymes might be used

yeah...but ya still gotta isolate it and purify it! So gel electrophorisis it, cut out your band of interest, and re-read my post.

 

maybe you can at a "rinse and repeat" cycle to this post.