What will be ploidy of definitive nucleus if the cross is made between 12n female plant and 10n male plant

Options

A. 17n
B. 22n
C. 11n
D. 12n

Answer

To determine the ploidy of the definitive nucleus formed from a cross between a 12n female plant and a 10n male plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ploidy of the Female Plant:**
- The female plant has a ploidy of 12n. This means that the sporophyte (the plant body) is 12n, which is diploid (2n) in terms of its chromosome number.

2. **Determine the Ploidy of the Female Gametes:**
- The female gametes (egg and polar nuclei) are formed through meiosis. Since the female plant is 12n, the gametes will be haploid (n) after meiosis.
- The ploidy of the female gametes will be 6n (12n/2 = 6n).

3. **Identify the Ploidy of the Male Plant:**
- The male plant has a ploidy of 10n. Similar to the female plant, the male sporophyte is also diploid (2n).

4. **Determine the Ploidy of the Male Gametes:**
- The male gametes are also formed through meiosis. Since the male plant is 10n, the male gametes will be haploid (n).
- The ploidy of the male gametes will be 5n (10n/2 = 5n).

5. **Formation of the Definitive Nucleus:**
- The definitive nucleus is formed when the two polar nuclei (from the female gametophyte) fuse together.
- Each polar nucleus will have a ploidy of 6n (as established earlier).

6. **Calculate the Ploidy of the Definitive Nucleus:**
- The definitive nucleus is formed by the fusion of two polar nuclei. Therefore, the ploidy of the definitive nucleus will be:
- 6n (from one polar nucleus) + 6n (from the other polar nucleus) = 12n.

7. **Conclusion:**
- Thus, the ploidy of the definitive nucleus formed from the cross between a 12n female plant and a 10n male plant is **12n**.

### Final Answer:
The ploidy of the definitive nucleus is **12n**.

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