Monohybrid cross produced both tall and dwarf Pea plants in the ratio of 3:1. Their genotypes would be

Options

A. `TT xxTt`
B. `Tt xxTt`
C. `Tt xx tt`
D. `TT xxtt`

Answer

To solve the question regarding the genotypes of pea plants in a monohybrid cross that produces a phenotypic ratio of 3:1 (tall to dwarf), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Phenotypes**:
- In this cross, we observe two phenotypes: tall plants and dwarf plants. The tall phenotype is dominant, while the dwarf phenotype is recessive.

2. **Identifying the Dominant and Recessive Alleles**:
- Let's denote the dominant allele for tall plants as **T** (capital T) and the recessive allele for dwarf plants as **t** (small t).

3. **Setting Up the Monohybrid Cross**:
- A monohybrid cross involves two individuals that differ in one trait. To achieve a 3:1 ratio, we need to cross two heterozygous tall plants (Tt) or one homozygous tall plant (TT) with one heterozygous tall plant (Tt).

4. **Crossing Two Heterozygous Tall Plants**:
- If we cross two heterozygous tall plants (Tt x Tt), we can set up a Punnett square:

```
T t
-------------
T | TT | Tt |
-------------
t | Tt | tt |
```

5. **Analyzing the Results**:
- From the Punnett square, we can see the genotypes of the offspring:
- 1 TT (homozygous tall)
- 2 Tt (heterozygous tall)
- 1 tt (homozygous dwarf)
- This results in a phenotypic ratio of 3 tall (TT and Tt) to 1 dwarf (tt).

6. **Conclusion**:
- Therefore, the genotypes of the parent plants that produce a 3:1 ratio of tall to dwarf pea plants in a monohybrid cross would be **Tt x Tt**.

### Final Answer:
The genotypes of the parent plants are **Tt x Tt**.

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