If pollen grain is having 12 chromosome then what would be the chromosomes number in endosperm of gymnosperm and angiosperm respectively?

Options

A. 24 and 36
B. 36 and 36
C. 12 and 36
D. 24 and 24

Answer

To solve the problem, we need to understand the relationship between the chromosome number in pollen grains, which represent the male gametes, and the endosperm in both gymnosperms and angiosperms.

### Step-by-Step Solution:

1. **Identify the Chromosome Number in Pollen Grains:**
- The question states that the pollen grain has 12 chromosomes. Since pollen grains are male gametes, they are haploid (n). Therefore, the chromosome number in the pollen grain is n = 12.

2. **Determine the Chromosome Number in the Zygote:**
- In both gymnosperms and angiosperms, fertilization occurs when the male gamete (pollen grain) fuses with the female gamete (ovule). The female gamete is also haploid (n).
- Thus, the zygote formed after fertilization will have a diploid chromosome number (2n).
- Since the male gamete contributes 12 chromosomes, the female gamete also contributes 12 chromosomes, resulting in a total of 2n = 12 + 12 = 24 chromosomes in the zygote.

3. **Understand the Formation of Endosperm:**
- In angiosperms, the endosperm is formed through a process called double fertilization. In this process, one sperm cell fertilizes the egg cell to form the zygote (2n), and another sperm cell fuses with two polar nuclei to form the endosperm.
- The endosperm is triploid (3n) in angiosperms. Therefore, the chromosome number in the endosperm will be 3n = 3 × 12 = 36 chromosomes.

4. **Determine the Chromosome Number in Gymnosperms:**
- In gymnosperms, the endosperm is formed from the female gametophyte, which is haploid (n). Thus, the endosperm in gymnosperms is also haploid and will have the same chromosome number as the pollen grain.
- Therefore, the chromosome number in the endosperm of gymnosperms will be n = 12.

### Final Answer:
- The chromosome number in the endosperm of gymnosperms is **12**.
- The chromosome number in the endosperm of angiosperms is **36**.