The essential observation made by Mendel in his experiments on inheritance in pea plants was that

Options

A. Parental characters that were not exhibited in the `F_(1)` generation reappeared in the `F_(2)`
B. Genetic information was encoded in DNA sequence
C. A3: 1 phenotypic ratio (dominant: recessive) was exhibited by the `F_(2)` generation
D. A3: 1 phenotypic ratio (recessive: dominant) was exhibited by the `F_(2)` generation.

Answer

**Step-by-Step Solution:**

1. **Understanding Mendel's Experiments**: Gregor Mendel conducted experiments on pea plants to study inheritance patterns. He focused on traits such as flower color, seed shape, and pod color.

2. **Observation of F1 Generation**: In Mendel's experiments, he crossed purebred plants with different traits (e.g., red flowers and white flowers). The offspring (F1 generation) displayed only the dominant trait (e.g., all red flowers).

3. **Reappearance in F2 Generation**: When Mendel allowed the F1 generation to self-pollinate, he observed that the recessive trait (white flowers) reappeared in the F2 generation. This was a crucial observation, indicating that the recessive traits were not lost but masked in the F1 generation.

4. **Conclusion on Dominance and Recessiveness**: Mendel concluded that traits are inherited as discrete units (now known as genes), and some traits can dominate over others. The essential observation was that the parental characters that did not appear in the F1 generation reappeared in the F2 generation.

5. **Identifying the Correct Option**: Among the options provided, the correct observation made by Mendel is that "Parental characters that were not exhibited in the F1 generation reappeared in the F2 generation."

**Final Answer**: The essential observation made by Mendel in his experiments on inheritance in pea plants was that parental characters that were not exhibited in the F1 generation reappeared in the F2 generation.

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