Which of the following components is required for the proper function fo DNA-dependent-DNA polymerase?
I. 4 different nucleotides
II. DNA template
III. An RNA primer

Options

A. (a) I only
B. (b) II and III only
C. (c) I and III only
D. (d) I,II, and III

Answer

To solve the question regarding the components required for the proper function of DNA-dependent DNA polymerase, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Understanding DNA-dependent DNA Polymerase**:
- DNA-dependent DNA polymerase is an enzyme that synthesizes DNA by using an existing DNA strand as a template. It is essential for DNA replication.

2. **Analyzing the Components**:
- **I. 4 different nucleotides**:
- DNA polymerase requires deoxyribonucleoside triphosphates (dNTPs) as the building blocks for DNA synthesis. These nucleotides are essential for adding new bases to the growing DNA strand.
- **Conclusion**: This component is required.

- **II. DNA template**:
- The enzyme needs a DNA template to guide the synthesis of the new DNA strand. The template strand provides the sequence information that the new strand will follow.
- **Conclusion**: This component is required.

- **III. An RNA primer**:
- DNA polymerase cannot initiate DNA synthesis on its own; it requires a primer. This primer is typically a short RNA sequence that provides a free 3'-OH group for the addition of dNTPs.
- **Conclusion**: This component is required.

3. **Final Evaluation**:
- Since all three components (4 different nucleotides, DNA template, and RNA primer) are necessary for the proper function of DNA-dependent DNA polymerase, we conclude that the correct answer includes all three components.

### Answer:
The correct answer is **D. All of the above (I, II, and III)**.

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