Choose the correct sequence representing the ploidy of Nucellus, Megaspore mother cell, Megaspore, Egg cell, Zygote: A polar nucleus of embryo sac, Secondary nucleus and Primary endosperm nucleus.

Options

A. n, 2n, 2n, n, 2n, n, 2n, and 2n
B. 2n, 2n, n, 2n, n, 2n, 3n, and 2n
C. 2n, 2n, n, n, 2n, n, 2n, and 3n
D. 2n, n, n, 2n, 3n, n, and 3n

Answer

To solve the question regarding the ploidy levels of various structures in flowering plants, we will analyze each component step by step.

### Step-by-Step Solution:

1. **Nucellus**:
- The nucellus is a tissue found within the ovule that surrounds the embryo sac. It is diploid (2n) because it is part of the ovule, which originates from the diploid sporophyte generation.
- **Ploidy Level**: Diploid (2n)

2. **Megaspore Mother Cell (MMC)**:
- The megaspore mother cell is also diploid (2n). It undergoes meiosis to produce megaspores.
- **Ploidy Level**: Diploid (2n)

3. **Megaspore**:
- The megaspore is produced from the megaspore mother cell through meiosis. It is haploid (n).
- **Ploidy Level**: Haploid (n)

4. **Egg Cell**:
- The egg cell is a female gamete, which is also haploid (n).
- **Ploidy Level**: Haploid (n)

5. **Zygote**:
- The zygote is formed by the fusion of the male and female gametes (sperm and egg). Since both gametes are haploid, their fusion results in a diploid (2n) zygote.
- **Ploidy Level**: Diploid (2n)

6. **Polar Nucleus of Embryo Sac**:
- The polar nuclei are found in the central cell of the embryo sac. Each polar nucleus is haploid (n), and there are typically two polar nuclei that can fuse to form a secondary nucleus.
- **Ploidy Level**: Haploid (n)

7. **Secondary Nucleus**:
- The secondary nucleus is formed by the fusion of the two polar nuclei. Therefore, it is diploid (2n).
- **Ploidy Level**: Diploid (2n)

8. **Primary Endosperm Nucleus**:
- The primary endosperm nucleus is formed after fertilization when the male gamete fuses with the secondary nucleus. Since the secondary nucleus is diploid (2n) and the male gamete is haploid (n), the resulting endosperm is triploid (3n).
- **Ploidy Level**: Triploid (3n)

### Summary of Ploidy Levels:
- Nucellus: Diploid (2n)
- Megaspore Mother Cell: Diploid (2n)
- Megaspore: Haploid (n)
- Egg Cell: Haploid (n)
- Zygote: Diploid (2n)
- Polar Nucleus: Haploid (n)
- Secondary Nucleus: Diploid (2n)
- Primary Endosperm Nucleus: Triploid (3n)

### Final Sequence of Ploidy Levels:
1. Nucellus - Diploid (2n)
2. Megaspore Mother Cell - Diploid (2n)
3. Megaspore - Haploid (n)
4. Egg Cell - Haploid (n)
5. Zygote - Diploid (2n)
6. Polar Nucleus - Haploid (n)
7. Secondary Nucleus - Diploid (2n)
8. Primary Endosperm Nucleus - Triploid (3n)