Double-helical structure is found in .................

Explanation

To answer the question "Double-helical structure is found in .................", we can follow these steps:

### Step 1: Understand the Concept of Double Helix
The double helix is a specific structural formation that consists of two strands that wind around each other. This structure is most commonly associated with DNA.

**Hint:** Think about the molecular structures that are known to have a double helical shape.

### Step 2: Identify the Molecule Associated with Double Helix
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