Mendel called the fundamental physical unit of heredity as

Options

A. Gene
B. Unit factor
C. Cistron
D. Operon

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks what Mendel referred to as the fundamental physical unit of heredity.

2. **Recall Mendel's Contributions**: Gregor Mendel is known as the father of genetics. He conducted experiments with pea plants and formulated the laws of inheritance.

3. **Understand the Terminology**:
- A "gene" is defined as a segment of DNA that contains the information for a specific trait.
- The term "unit factor" is also associated with Mendel’s work, but it is not the term he used to describe the fundamental physical unit of heredity.
- "Cistron" and "operon" are terms used in molecular biology but are not directly related to Mendel’s original terminology.

4. **Select the Correct Answer**: Based on Mendel's work and the definitions of the terms, the correct answer is "gene." Mendel referred to genes as the fundamental physical units of heredity.

5. **Final Answer**: Mendel called the fundamental physical unit of heredity as **gene**.

---