A piece of nucleic acid used to find the sequence of bases in a gene, by forming a hybrid with it, is called

Options

A. retrogene
B. vector
C. carrier
D. DNA probe

Answer

To solve the question, "A piece of nucleic acid used to find the sequence of bases in a gene, by forming a hybrid with it, is called," we will analyze the options provided and determine the correct answer step by step.

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for a specific term that describes a piece of nucleic acid that can hybridize with a gene to identify its base sequence.

2. **Evaluate the Options**:
- **Option A: Retro Gene**: A retro gene is a processed copy of another gene, typically referring to a gene that has been reverse transcribed from RNA. This does not fit the description of a nucleic acid used for hybridization. **(Incorrect)**

- **Option B: Vector**: A vector is a DNA molecule used to carry foreign genetic material into another cell. While vectors are important in genetic engineering, they do not specifically refer to a nucleic acid used for finding sequences in genes. **(Incorrect)**

- **Option C: Carrier**: A carrier refers to an individual who carries a genetic mutation but does not specifically relate to nucleic acids or hybridization. Therefore, this option is not relevant to the question. **(Incorrect)**

- **Option D: DNA Probe**: A DNA probe is a piece of single-stranded DNA that is complementary to the target sequence in a gene. It is used to detect the presence of this sequence by hybridizing with it. This matches the description given in the question. **(Correct)**

3. **Conclusion**: After evaluating all the options, the correct answer is **DNA Probe**.

### Final Answer:
The correct term is **DNA Probe**.

---