Experimental verification of chromosomal theory of inheritance was given by

Options

A. Thomas Hunt Morgan
B. Gregor Johann Mendel
C. Hugo de vries
D. Langdon Down

Answer

### Step-by-Step Solution:

1. **Identify the Question**: The question asks who provided the experimental verification of the chromosomal theory of inheritance.

2. **Recall Key Figures in Genetics**: The options provided include Thomas Hunt Morgan, Grieger, John and Mendel, Hugo de Vries, and Langdon Downs. It is essential to recall the contributions of these scientists to genetics.

3. **Focus on Thomas Hunt Morgan**: Thomas Hunt Morgan is well-known for his work with Drosophila (fruit flies) and is credited with significant contributions to the understanding of inheritance patterns.

4. **Understand Morgan's Experiments**: Morgan conducted experiments that demonstrated that genes are located on chromosomes. He specifically studied sex-linked traits in Drosophila and observed that certain traits did not segregate independently, which contradicted Mendel's law of independent assortment.

5. **Conclusion**: Based on Morgan's findings and his role in verifying the chromosomal theory of inheritance, the correct answer to the question is Thomas Hunt Morgan.

### Final Answer:
The experimental verification of the chromosomal theory of inheritance was given by **Thomas Hunt Morgan**.

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