Pure tall plant is crossed to dwarf plant. `F_(1)` generation consists of only tall plants while `F_(2)` generation has both tall and dwarf in ratio of 3:1. The phenomenon is due to

Options

A. Dominance
B. Codominance
C. Incomplete dominance
D. Heredity

Answer

To solve the question, we need to analyze the genetic cross between a pure tall plant and a dwarf plant, and understand the inheritance patterns observed in the F1 and F2 generations.

### Step-by-Step Solution:

1. **Identify the Parent Plants**:
- We have two parent plants: one is a pure tall plant (homozygous dominant, TT) and the other is a dwarf plant (homozygous recessive, tt).

2. **Cross the Parent Plants**:
- When we cross the pure tall plant (TT) with the dwarf plant (tt), all offspring in the F1 generation will inherit one allele from each parent.
- The resulting genotype of the F1 generation will be Tt (heterozygous).

3. **Phenotype of the F1 Generation**:
- Since the tall trait (T) is dominant over the dwarf trait (t), all plants in the F1 generation will exhibit the tall phenotype. Thus, the F1 generation consists only of tall plants.

4. **Self-Cross the F1 Generation**:
- Next, we self-cross the F1 generation (Tt x Tt) to produce the F2 generation.

5. **Gamete Formation**:
- Each F1 plant can produce two types of gametes: T and t. When we cross Tt with Tt, we can set up a Punnett square to determine the possible genotypes of the F2 generation.

6. **Punnett Square Analysis**:
- The Punnett square will yield the following combinations:
- TT (tall)
- Tt (tall)
- Tt (tall)
- tt (dwarf)
- This results in a genotypic ratio of 1 TT : 2 Tt : 1 tt.

7. **Phenotypic Ratio in F2 Generation**:
- The phenotypic ratio of the offspring in the F2 generation will be 3 tall (TT and Tt) to 1 dwarf (tt). Therefore, the ratio is 3:1.

8. **Conclusion**:
- The observed phenomenon is due to the principle of dominance, where the dominant trait (tall) masks the expression of the recessive trait (dwarf) in the F1 generation and results in a characteristic 3:1 ratio in the F2 generation.

### Final Answer:
The phenomenon is due to **dominance**.

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