Synapsis occurs between

Options

A. Spindle fibres and centromere
B. Two homologous chromosomes
C. A male and a female gamete
D. mRNA and ribosomes

Answer

**Step-by-Step Solution:**

1. **Understanding Synapsis**: Synapsis is the process where homologous chromosomes pair up during meiosis. It is a crucial step in the formation of gametes.

2. **Identifying Homologous Chromosomes**: Homologous chromosomes are pairs of chromosomes that have the same structure and gene sequence but may have different alleles. Each pair consists of one chromosome from the mother and one from the father.

3. **Diagram Representation**: To visualize this, we can draw two homologous chromosomes. Each chromosome consists of two sister chromatids connected at a region called the centromere.

4. **Formation of Chiasma**: During synapsis, the homologous chromosomes align closely along their lengths, and points of contact called chiasmata form. This is where genetic material can be exchanged between the chromatids of the homologous chromosomes.

5. **Crossing Over**: The process of exchanging genetic material at the chiasma is known as crossing over. This contributes to genetic variation in the offspring.

6. **Location of Synapsis**: Synapsis occurs during Prophase I of meiosis, specifically in the zygotene stage, where the homologous chromosomes are paired.

7. **Conclusion**: Therefore, synapsis occurs between two homologous chromosomes, making option B the correct answer.

---