The double helical structure of DNA was proposed by

Options

A. Watson and Crick
B. Meicher
C. Emil Fischer
D. Khorana

Answer

To solve the question regarding who proposed the double helical structure of DNA, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks who proposed the double helical structure of DNA. This structure is fundamental to understanding the molecular basis of genetics.

2. **Identify Key Contributors**: The most significant contributors to the discovery of the DNA structure are James Watson and Francis Crick. They are well-known for their work in molecular biology.

3. **Recall Historical Context**: In 1953, Watson and Crick published their findings on the structure of DNA, which they described as a double helix. This was a groundbreaking discovery in the field of genetics.

4. **Confirm the Answer**: Based on historical records and scientific literature, it is widely accepted that the double helical structure of DNA was proposed by James Watson and Francis Crick.

5. **Select the Correct Option**: From the options provided, the correct answer is "Watson and Crick."

### Final Answer:
The double helical structure of DNA was proposed by Watson and Crick.

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