DNA precipitation out of a mixture of biomolecules can be achieved by treatment with:

Options

A. Isopropanol
B. Chilled ethanol
C. Methanol at room temperature
D. Chilled chlo

Answer

To answer the question about how DNA precipitation out of a mixture of biomolecules can be achieved, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding DNA Precipitation**: DNA precipitation is a process used to isolate DNA from a mixture of biomolecules. This is typically done by altering the solubility of DNA in the solution.

2. **Role of Alcohols**: Alcohols such as ethanol and isopropanol are commonly used for DNA precipitation. They help to reduce the solubility of DNA in the solution.

3. **Chilled Ethanol**: Among the options provided, chilled ethanol is particularly effective for DNA precipitation. Ethanol is less polar than water, which means it disrupts the hydration shell around the DNA molecules.

4. **Dielectric Constant**: The dielectric constant of ethanol is significantly lower than that of water (24.3 for ethanol at 25°C), which means that when ethanol is added to a solution containing DNA, it reduces the shielding effect of water on the DNA's negative charges.

5. **Presence of Cations**: For effective DNA precipitation, it is also important to have cations present in the solution (such as Na⁺, NH₄⁺, or Li⁺) to neutralize the negative charges on the DNA, facilitating its aggregation and precipitation.

6. **Conclusion**: Therefore, the correct treatment for precipitating DNA from a mixture of biomolecules is chilled ethanol.

### Final Answer:
The correct treatment for DNA precipitation out of a mixture of biomolecules is **chilled ethanol**.

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