A typical embryo sac is

Options

A. 8-nucleated and 7-celled
B. 7-nucleated and 7-celled
C. 8-nucleated and 8-celled
D. 7-nucleated and 8-celled

Answer

To answer the question "A typical embryo sac is," we need to understand the structure of a mature embryo sac in angiosperms. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Definition of Embryo Sac**:
- The embryo sac is the female gametophyte in angiosperms (flowering plants) where fertilization occurs.

2. **Nuclear Composition**:
- A typical mature embryo sac contains **8 nuclei**. This is because there are two polar nuclei in the center that fuse to form a diploid secondary nucleus.

3. **Cellular Composition**:
- The embryo sac is composed of **7 cells**. This includes:
- **1 egg cell** (female gamete)
- **2 synergid cells** (which help in guiding the pollen tube during fertilization)
- **3 antipodal cells** (located at the chalazal end)
- The two polar nuclei are located in the center, which do not form separate cells but contribute to the total count of nuclei.

4. **Conclusion**:
- Therefore, the typical embryo sac is characterized as **8 nucleated and 7 celled**.

### Final Answer:
- A typical embryo sac is **8 nucleated and 7 celled**.

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