Mendel's monohybrid ratio is -

Options

A. `1:2`
B. `3:1`
C. `9: 3:3:1`
D. `9:7`

Answer

### Step-by-Step Solution:

1. **Understanding Monohybrid Cross**: A monohybrid cross involves a single trait that is being studied, where two parents differ in one characteristic. For example, Mendel studied the height of pea plants, where one parent was tall (dominant trait) and the other was dwarf (recessive trait).

2. **F1 Generation**: When Mendel crossed a tall plant (TT) with a dwarf plant (tt), all the offspring (F1 generation) were tall (Tt). This shows that the tall trait is dominant over the dwarf trait.

3. **F2 Generation**: When the F1 plants (Tt) were self-fertilized, the F2 generation was produced. The genotypes of the F2 generation can be TT, Tt, and tt.

4. **Genotypic Ratio**: The genotypic ratio of the F2 generation is 1 TT : 2 Tt : 1 tt.

5. **Phenotypic Ratio**: The phenotypic ratio, which shows the observable traits, is 3 tall (TT and Tt) : 1 dwarf (tt). This is known as Mendel's monohybrid ratio.

6. **Conclusion**: Therefore, Mendel's monohybrid ratio is 3:1, indicating that in a typical monohybrid cross, three offspring will exhibit the dominant trait for every one offspring that exhibits the recessive trait.