Question

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

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

Answer 1

The Correct Option is C

In recombinant DNA technology, the purification of nucleic acids is a crucial step. One common method used to precipitate nucleic acids is the addition of chilled ethanol.

Here's how the process works:

1. Nucleic acids such as DNA and RNA are often soluble in aqueous solutions. This solubility is due to their hydrophilic nature.
2. To precipitate these nucleic acids, solvents like ethanol or isopropanol are used. When cold ethanol is added to an aqueous solution containing DNA, it reduces the solubility of the DNA.
3. Chilled ethanol reduces the dielectric constant of the solution, causing the negatively charged DNA molecules to aggregate and precipitate out of the solution.

Let's consider the given options:

• Polysaccharides: While polysaccharides can also be precipitated in alcohol, the efficiency is typically lower compared to nucleic acids.
• RNA: RNA can also be precipitated using ethanol; however, in this context, the focus is primarily on DNA precipitation during recombinant DNA purification processes.
• DNA: This is indeed the target molecule for precipitation during the purification process in recombinant DNA technology. Chilled ethanol effectively precipitates DNA, making it the correct answer.
• Histones: These are proteins, and they do not precipitate with ethanol as nucleic acids do.

Conclusion: The addition of chilled ethanol in the purification process for recombinant DNA technology specifically precipitates out DNA, making it the correct answer.