Wheat root cells have 42 chromosomes. The number of chromosomes in a cell of pollen grain is

Options

A. 14
B. 21
C. 28
D. 42

Answer

To determine the number of chromosomes in a cell of a pollen grain from the given information about wheat root cells, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chromosome Number in Wheat Root Cells**:
- We know that wheat root cells have 42 chromosomes. This indicates that these cells are diploid (2n), meaning they contain two sets of chromosomes.

2. **Meiosis and Pollen Grain Formation**:
- Pollen grains are formed from the male gametophyte, which develops from microspores. The microspore mother cell undergoes meiosis to produce microspores.

3. **Chromosome Number in Microspores**:
- Since the microspore mother cell is diploid (2n), after meiosis, the resulting microspores will be haploid (n). This means they will have half the number of chromosomes compared to the diploid cells.

4. **Calculating the Number of Chromosomes in Pollen Grains**:
- Given that the wheat root cells have 42 chromosomes (2n), the haploid number of chromosomes in the pollen grain will be:
\[ \text{Haploid number (n)} = \frac{42}{2} = 21 \]

5. **Conclusion**:
- Therefore, the number of chromosomes in a cell of pollen grain is 21.

### Final Answer:
The number of chromosomes in a cell of pollen grain is **21**.

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