A phenotypic ratio not obtained by Mendel was

Options

A. `3:1`
B. `1:2:1`
C. `1:1:1:1`
D. `9:3:3:1`

Answer

To determine a phenotypic ratio that was not obtained by Mendel, we need to analyze the ratios he discovered through his experiments with monohybrid and dihybrid crosses.

### Step-by-Step Solution:

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

2. **Identify Ratios from Mendel's Crosses**:
- **Monohybrid Cross**: When Mendel crossed plants differing in one trait, he observed a phenotypic ratio of **3:1** in the offspring. This means that for every three offspring showing the dominant trait, there was one showing the recessive trait.
- **Dihybrid Cross**: When he crossed plants differing in two traits, he observed a phenotypic ratio of **9:3:3:1**. This ratio represents the combinations of the dominant and recessive traits for both characteristics.

3. **Consider Other Ratios**:
- **Genotypic Ratio in Monohybrid Cross**: This ratio is **1:2:1**.
- **Linkage Phenomenon**: When genes are linked, they do not assort independently, leading to a different ratio. In such cases, a phenotypic ratio of **1:1:1:1** can be observed, but this occurs only when the genes are linked.

4. **Conclusion**:
- The ratios obtained by Mendel include **3:1** for monohybrid crosses and **9:3:3:1** for dihybrid crosses. However, the **1:1:1:1** ratio is not one that Mendel observed because it arises from linked genes, which he did not encounter in his studies.

5. **Final Answer**:
- The phenotypic ratio not obtained by Mendel is **1:1:1:1**.