A cross between two tall plants resulted in offspring having few dwarf plants. What would be the genotypes of both the parents?

Options

A. TT and Tt
B. Tt and Tt
C. TT and TT
D. Tt and tt

Explanation

To determine the genotypes of the parents in the given scenario, we need to analyze the information provided about the offspring resulting from the cross between two tall plants. Here’s a step-by-step solution:

### Step 1: Understand the Traits
- **Tall plants** are represented by the dominant allele **T** (capital T).
- **Dwarf plants** are represented by the recessive allele **t** (small t).

### Step 2: Analyze the Offspring
- The offspring from the cross of two tall plants include some dwarf plants. This indicates that both parents must carry the recessive allele **t** in their genotype, as dwarf plants can only arise when both alleles are recessive (tt).

### Step 3: Determine Possible Genotypes of Parents
- The possible genotypes for tall plants can be:
1. **TT** (homozygous dominant)
2. **Tt** (heterozygous)

Since dwarf plants (tt) are present in the offspring, both parents must be heterozygous **Tt**. If either parent were homozygous **TT**, all offspring would be tall (TT or Tt), and no dwarf plants would appear.

### Step 4: Set Up the Punnett Square
- To confirm, we can set up a Punnett square for a cross between two **Tt** parents:

| | T | t |
|-----|-----|-----|
| **T** | TT | Tt |
| **t** | Tt | tt |

### Step 5: Analyze the Results
- The results from the Punnett square show:
- 1 TT (tall)
- 2 Tt (tall)
- 1 tt (dwarf)

This results in a phenotypic ratio of 3 tall plants to 1 dwarf plant, which matches the observation of the offspring.

### Conclusion
- Therefore, the genotypes of both parents must be **Tt** (heterozygous tall).

### Final Answer
The genotypes of both parents are **Tt** and **Tt**.

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