One gene-one enzyme hypothesis has been changed to .................... .

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Original Hypothesis:**
- The original hypothesis proposed by Beadle and Tatum is known as the "one gene-one enzyme hypothesis." This suggests that each gene is responsible for the production of a specific enzyme.

2. **Limitations of the Original Hypothesis:**
- This hypothesis was later found to be limited because not all proteins produced by genes are enzymes. While enzymes are proteins, many proteins serve other functions (e.g., structural roles).

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