X-chromosomes or X-body was first observed by

Options

A. Mendel-1901
B. Castle-1910
C. Henking-1891
D. Bateson-1906

Answer

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks about who first observed the X-chromosome or X-body.

2. **Reviewing the Options**: The options provided are:
- A) Mendel
- B) Kessel
- C) Henking
- D) Watson

3. **Analyzing Each Scientist's Contribution**:
- **Mendel**: Gregor Mendel is known as the father of genetics. He conducted experiments on pea plants and formulated the laws of inheritance. However, he did not work on chromosomes or the X-chromosome specifically.

- **Kessel**: Kessel's work involved grafting techniques in plants and animals. His contributions are significant in the field of botany and animal science, but he did not discover the X-chromosome.

- **Henking**: Hermann Henking was a biologist who studied the reproductive cells (sperm) and is credited with the discovery of the X-chromosome (or X-body) in insects. His experiments led to the identification of this chromosome.

- **Watson**: James Watson is known for his role in the discovery of the structure of DNA. He coined the term "pure line" in genetics, but he did not discover the X-chromosome.

4. **Identifying the Correct Answer**: Based on the contributions of each scientist, the correct answer is **C) Henking**, as he was the one who first observed the X-chromosome.

### Final Answer:
The X-chromosome or X-body was first observed by **Henking**.

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