Due to the activity of recombinase enzyme, an X-shaped structure is observed between non-sister chromatids of homologous chromosomes. This is known as :-

Options

A. Diad
B. Bivalent
C. Synaptonemal complex
D. Chiasmata

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: The question refers to a specific structure formed during the process of meiosis, particularly during the pachytene stage. This stage is crucial for genetic recombination.

2. **Identifying the Enzyme**: The enzyme mentioned is the recombinase enzyme. Its role is to facilitate the exchange of genetic material between non-sister chromatids of homologous chromosomes.

3. **Defining Homologous Chromosomes**: Homologous chromosomes are pairs of chromosomes that have the same structure and gene sequence but may carry different alleles (variations of a gene). Each chromosome in a homologous pair comes from one parent.

4. **Recognizing Chromatids**: In the context of meiosis, each chromosome consists of two sister chromatids (identical copies). However, during recombination, we focus on non-sister chromatids, which belong to different homologous chromosomes.

5. **Formation of the X-shaped Structure**: During the pachytene stage, the non-sister chromatids of homologous chromosomes come close together and undergo a process called crossing over. This process results in an exchange of genetic material and forms an X-shaped structure.

6. **Naming the Structure**: The X-shaped structure formed during this exchange of genetic material between non-sister chromatids is known as a "chiasma."

7. **Final Answer**: Therefore, the structure observed due to the activity of the recombinase enzyme between non-sister chromatids of homologous chromosomes is called a **chiasma**.

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