Question

During the purification process for recombinant DNA technology, addition of chilled ethanol precipitates out :

• A. Polysaccharides
• B. RNA
• C. DNA
• D. Histones

Answer 1

The correct option is C DNA

The first step in recombinant DNA technology is the isolation of genetic material which is DNA in majority of the organisms.
In order to use the DNA in the further steps, it is required to be in pure form, free from other macro-molecules.
Since the DNA is enclosed within the membranes, the cell has to be broken open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids.
It is achieved by treating the bacterial cells/plant or animal tissue with enzymes, such as lysozyme for bacterial cells, cellulase for plant cells and chitinase for fungal cells.
DNA is interwined with proteins such as histones which can be removed by treatment with proteases.
The RNA can be removed by treatment with ribonuclease.
Polysaccharides can be removed by treatment with carbohydrases.
On addition of chilled ethanol, purified DNA precipitates out. It can be seen as collection of fine threads in the suspension which can be removed by spooling.