Which substance would you add to cause precipitation of purified DNA from a solution?

Options

A. Ether
B. Chilled ethanol
C. Taq. DNA polymerase
D. Chilled methanol

Answer

To answer the question of which substance would cause the precipitation of purified DNA from a solution, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of DNA Precipitation**:
- DNA precipitation is a crucial step in DNA extraction where the DNA is separated from the solution to obtain a pure form.

2. **Identify Common Reagents Used for DNA Precipitation**:
- Common reagents for precipitating DNA include alcohols such as ethanol and isopropanol.

3. **Evaluate the Options Provided**:
- The options given are ether, chilled ethanol, taq DNA polymerase, and chilled methanol.
- Ether is typically used for removing phenol and not for precipitating DNA.
- Taq DNA polymerase is an enzyme used in PCR and does not precipitate DNA.
- Chilled methanol is not commonly used for DNA precipitation.

4. **Choose the Correct Substance**:
- Chilled ethanol is widely recognized as the reagent that effectively precipitates DNA from solution. When chilled ethanol is added, DNA forms visible fine threads that can be collected.

5. **Conclusion**:
- Therefore, the correct answer to the question is **chilled ethanol**.