The only structural pattern that has been found among isometric viruses is

Options

A. icosahedral
B. spherical
C. helical
D. tetrahedral

Answer

To solve the question regarding the only structural pattern found among isometric viruses, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Term "Isometric Viruses":**
- Isometric viruses are viruses that have a symmetrical structure. They typically exhibit a spherical shape and are characterized by their geometric arrangement.

2. **Identify the Structural Patterns:**
- The options given are:
- Option 1: Icosahedral
- Option 2: Aspherical
- Option 3: Helical
- Option 4: Tetrahedral

3. **Analyze Each Option:**
- **Icosahedral:** This is a common structural pattern for many isometric viruses. It consists of 20 equilateral triangular faces, which gives it a spherical appearance.
- **Aspherical:** This term suggests a lack of a defined shape, which does not apply to isometric viruses.
- **Helical:** Helical viruses have a spiral structure, which is not characteristic of isometric viruses.
- **Tetrahedral:** This structure has 4 triangular faces, which is not a common pattern for isometric viruses.

4. **Conclusion:**
- Based on the analysis, the only structural pattern that has been found among isometric viruses is **icosahedral**.

### Final Answer:
The only structural pattern that has been found among isometric viruses is **icosahedral**.

---