Biotechnology- Principles and Processes Question 25
25. During the process of isolation of DNA, chilled ethanol is added to
[NEET Kar. 2013]
(a) Remove proteins such as histones
(b) Precipitate DNA
(c) Break open the cell to release DNA
(d) Facilitate action of restriction enzymes
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Answer : b
Hints & Solutions
(b) Ethanol is non-polar molecule while DNA is a polar molecule, it has a net negative charge due to the phosphate groups attached to it. When DNA is placed into a solution of $100 %$ ethanol, it becomes insoluble and precipitates out of solution. The role of alcohol in DNA extraction is to precipitate DNA into a visible form. The salts neutralize the negative charge of the negatively charged phosphate in DNA and the isopropanol /ethanol removes the hydration shell of $H 2 O$ molecules around the phosphate.
