A homogamous tall pistilltate plant (TT) is crossed with homogamous dwarf staminate plant (tt). What is the genotype of endosperm?

Options

A. TTT
B. TTt
C. Ttt
D. ttt

Answer

To determine the genotype of the endosperm resulting from the cross between a homogamous tall pistillate plant (TT) and a homogamous dwarf staminate plant (tt), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Parent Genotypes**:
- The pistillate plant (female) has the genotype **TT** (homozygous tall).
- The staminate plant (male) has the genotype **tt** (homozygous dwarf).

2. **Understand Double Fertilization**:
- In flowering plants, double fertilization occurs, which involves two fertilization events:
- **Syngamy**: The fusion of one male gamete with one female gamete to form the zygote.
- **Triple Fusion**: The fusion of the second male gamete with the diploid secondary nucleus of the ovule to form the triploid endosperm.

3. **Determine Gametes**:
- The female gamete from the pistillate plant (TT) will be **T** (since both alleles are T).
- The male gametes from the staminate plant (tt) will be **t** (since both alleles are t).

4. **Formation of the Zygote**:
- The zygote is formed by the fusion of one male gamete (t) and one female gamete (T):
- Zygote genotype: **Tt** (heterozygous).

5. **Formation of the Endosperm**:
- The triploid endosperm is formed by the fusion of the second male gamete (t) with the diploid secondary nucleus (TT):
- Endosperm genotype: **TT + t = TTT** (which simplifies to **Tt**).

6. **Final Genotype of the Endosperm**:
- The endosperm will have the genotype **Tt** (triploid, as it consists of one T from the female and two t from the male gametes).

### Conclusion:
The genotype of the endosperm resulting from this cross is **Tt**.

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