In human females, meiosis-II is not completed until

Options

A. Uterine implantation
B. Birth
C. Puberty
D. Fertilisation

Answer

**Step-by-Step Solution:**

1. **Understanding Oogenesis**: In human females, the process of gametogenesis is called oogenesis, which is responsible for the formation of ova (egg cells).

2. **Primordial Germ Cells**: The process begins with primordial germ cells known as oogonia, which are diploid (2n) in nature.

3. **Formation of Primary Oocyte**: Oogonia undergo mitotic division to form primary oocytes, which are also diploid.

4. **Meiosis I**: The primary oocyte then undergoes the first meiotic division (meiosis I) to produce a secondary oocyte and a polar body. At this stage, the secondary oocyte is haploid (n).

5. **Arrest in Meiosis II**: The secondary oocyte is formed at the onset of puberty and is arrested in the second meiotic division (meiosis II). This means that meiosis II is not completed until a specific event occurs.

6. **Completion of Meiosis II**: Meiosis II is completed only upon fertilization. When a sperm cell penetrates the secondary oocyte, meiosis II resumes and completes, resulting in the formation of the ovum and another polar body.

7. **Conclusion**: Therefore, in human females, meiosis II is not completed until fertilization occurs.

**Final Answer**: In human females, meiosis II is not completed until fertilization.

---