Which chemical is used to obtain a precipitate of pure DNA?

Options

A. Methanol
B. Ether
C. HCl
D. Ethanol

Explanation

To obtain a precipitate of pure DNA, the chemical used is ethanol. Here's a step-by-step explanation of the process:

### Step-by-Step Solution:

1. **Understanding DNA Extraction**: The process of obtaining pure DNA from cells involves breaking down the cell membrane and separating the DNA from other cellular components.

2. **Cell Lysis**: Initially, a lysis buffer is used to break open the cells. This buffer typically contains detergents that disrupt the lipid bilayer of the cell membrane, releasing the DNA into the solution.

3. **Removal of Proteins and Debris**: After lysis, proteins and other cellular debris are removed, often using a protease enzyme or by centrifugation.

4. **Precipitation of DNA**: To precipitate the DNA from the solution, a cold alcohol is added. Ethanol is commonly used for this purpose because it reduces the solubility of DNA in the solution.

5. **Centrifugation**: After adding ethanol, the mixture is centrifuged. This process causes the DNA to aggregate and form a visible precipitate at the bottom of the tube.

6. **Collection of DNA**: The precipitated DNA can then be collected by carefully removing the supernatant and washing the DNA pellet with alcohol to remove any remaining impurities.

7. **Drying and Resuspension**: Finally, the DNA pellet is dried and resuspended in a suitable buffer or water for further analysis or use.

### Final Answer:
The chemical used to obtain a precipitate of pure DNA is **ethanol**.

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