During the studies on genes in Drosophila that were sex-linked T.H. Morgan found F2-population phenotypic ratios deviated from expected 9 : 3 : 3 : 1. Explain the conclusion he arrived at.

Explanation

**Step-by-Step Solution:**

1. **Introduction to Mendelian Genetics**:
- Gregor Mendel established the foundational principles of genetics through his experiments with pea plants. He identified the phenotypic ratios for monohybrid and dihybrid crosses. The dihybrid cross typically yields a phenotypic ratio of 9:3:3:1, which represents the inheritance of two traits that assort independently.

**Hint**: Recall the basic principles of Mendelian genetics, particularly the ratios from monohybrid and dihybrid crosses.

2. **T.H. Morgan's Experiments with Drosophila**:
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