Which one of the following is not a diploid cell ?

Options

A. Zygote
B. Microspore mother cell
C. Primary oocyte
D. Ovum

Answer

To determine which of the following options is not a diploid cell, we will analyze each option provided in the question:

1. **Zygote**:
- A zygote is formed by the fusion of a male gamete (sperm) and a female gamete (egg).
- Both gametes are haploid (having one set of chromosomes).
- When they fuse, they form a zygote, which is diploid (having two sets of chromosomes).
- Therefore, the zygote is a diploid cell.

2. **Microspore Mother Cell**:
- The microspore mother cell, also known as microsporocyte, is found in plants.
- It is a diploid cell that undergoes meiosis to produce four haploid microspores.
- Thus, the microspore mother cell is also a diploid cell.

3. **Primary Oocyte**:
- A primary oocyte is found in human females and is formed from the oogonium, which is a diploid cell.
- The primary oocyte is also diploid as it is formed through mitotic division.
- It undergoes meiosis to eventually form a secondary oocyte and polar bodies, but the primary oocyte itself is diploid.

4. **Ovum**:
- An ovum is the female gamete that is formed from the primary oocyte after meiosis.
- The ovum is haploid, meaning it has only one set of chromosomes.
- Therefore, the ovum is not a diploid cell.

**Conclusion**: The option that is not a diploid cell is the **ovum**.