In case of inheritance of one gane, `3:1` phenotypic ratio can be explained on the basis of-

Options

A. Incomplete dominance
B. Condominance
C. Dominance
D. Linkage

Answer

To explain the 3:1 phenotypic ratio in the inheritance of one gene, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Basics of Inheritance**:
- Inheritance of traits is governed by genes, which can exist in different forms called alleles. Each individual has two alleles for each gene, one inherited from each parent.

2. **Identifying Dominant and Recessive Alleles**:
- Alleles can be classified as dominant or recessive. The dominant allele is expressed in the phenotype even if only one copy is present, while the recessive allele is expressed only when two copies are present.

3. **Setting Up a Monohybrid Cross**:
- When studying the inheritance of a single trait (monohybrid cross), we can use a classic example, such as the pea plants studied by Gregor Mendel.
- For instance, let’s consider a trait where "T" represents the dominant allele for tall plants and "t" represents the recessive allele for short plants.

4. **F1 Generation**:
- When we cross two homozygous parents (TT x tt), all offspring in the F1 generation will be heterozygous (Tt) and exhibit the dominant phenotype (tall).

5. **F2 Generation**:
- If we then self-cross the F1 generation (Tt x Tt), we can use a Punnett square to predict the genotypes of the offspring in the F2 generation.
- The possible combinations will be:
- TT (homozygous dominant)
- Tt (heterozygous)
- Tt (heterozygous)
- tt (homozygous recessive)

6. **Calculating the Phenotypic Ratio**:
- From the Punnett square, we find that:
- 3 plants will be tall (TT and Tt)
- 1 plant will be short (tt)
- This gives us a phenotypic ratio of 3:1 (tall:short).

7. **Conclusion**:
- Therefore, the 3:1 phenotypic ratio can be explained by the principle of dominance, where the dominant allele masks the expression of the recessive allele in the phenotype.

### Final Answer:
The 3:1 phenotypic ratio in the inheritance of one gene can be explained on the basis of **dominance**.

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