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 "Which substance would you add to cause precipitation of purified DNA from a solution?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding DNA Precipitation**:
- DNA precipitation is a common laboratory technique used to isolate DNA from a solution. It typically involves the addition of alcohol to the DNA solution, which causes the DNA to aggregate and precipitate out of the solution.

2. **Identifying Suitable Alcohols**:
- The two most commonly used alcohols for DNA precipitation are ethanol and isopropanol. Chilled ethanol is particularly effective because it helps to reduce the solubility of DNA.

3. **Evaluating the Options**:
- **Ether**: This is not typically used for DNA precipitation; it is more relevant for purifying high molecular weight DNA.
- **Chilled Ethanol**: This is the correct choice as it is widely used to precipitate DNA from a solution.
- **Taq DNA Polymerase**: This is an enzyme used in PCR (Polymerase Chain Reaction) and does not play a role in DNA precipitation.
- **Chilled Methanol**: While methanol can be used in some contexts, it is not the standard choice for DNA precipitation.

4. **Conclusion**:
- The substance that should be added to cause precipitation of purified DNA from a solution is **Chilled Ethanol**.

### Final Answer:
**Chilled Ethanol**

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