An animal cell was grown in a culture medium containing `P^(32)` nucleotides, the parts from which DNA is built. Later examination of the cell showed the radioactivity to be concentrated in the

Options

A. Golgi body
B. nucleus
C. rough ER
D. smooth ER

Answer

To solve the question regarding the concentration of radioactivity in an animal cell grown in a culture medium containing \( P^{32} \) nucleotides, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding \( P^{32} \) Nucleotides**:
- \( P^{32} \) is a radioactive isotope of phosphorus. It is commonly used as a tracer in biological experiments because it can be incorporated into nucleic acids (DNA and RNA).

2. **Identifying the Role of Nucleotides**:
- Nucleotides are the building blocks of nucleic acids. When \( P^{32} \) nucleotides are introduced into a culture medium, they will be incorporated into the DNA and RNA of the cells.

3. **Examining Cell Structures**:
- The question asks where the radioactivity from \( P^{32} \) is concentrated after the cell has been grown in this medium. The main cellular structures to consider are:
- **Nucleus**: Contains the cell's genetic material (DNA).
- **Golgi Body**: Involved in packaging and modifying proteins, not primarily involved in nucleic acid synthesis.
- **Rough Endoplasmic Reticulum (RER)**: Associated with protein synthesis, contains ribosomes, but does not contain DNA.
- **Smooth Endoplasmic Reticulum (SER)**: Involved in lipid synthesis, does not contain DNA.

4. **Determining the Location of Radioactivity**:
- Since \( P^{32} \) nucleotides are incorporated into nucleic acids, the location where the radioactivity will be concentrated is where DNA and RNA are found. The nucleus is the primary site for DNA, and it also contains RNA.

5. **Conclusion**:
- Based on the above analysis, the radioactivity from \( P^{32} \) nucleotides will be concentrated in the **nucleus** of the animal cell.

### Final Answer:
The radioactivity will be concentrated in the **nucleus**.

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