The `F_(2)` progeny of a monohybrid cross showed phenotypic and genotypic ratio as 1:2:1 , unlike that of Mendel's monohybrid `F_(2)` ratio. With the help of a suitable example, work out a cross and explain how it is possible.

Explanation

To solve the problem of explaining how the F2 progeny of a monohybrid cross can show a phenotypic and genotypic ratio of 1:2:1, we can use the example of the plant Mirabilis jalapa (commonly known as the four o'clock plant) to illustrate this phenomenon of incomplete dominance.

### Step-by-Step Solution:

1. **Understanding Monohybrid Cross**:
- A monohybrid cross involves a single trait controlled by one gene with two alleles. In Mendel's classic experiments, the dominant allele completely masks the effect of the recessive allele.

2. **Identifying the Alleles**:
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