Chiasmata are formed as a result of
(a) Exchange of pairs of paired homologous chromosomes
(b) Exchange of part of unpaired non-homologous chromosomes
(c) Duplication of parts of pairs of paired homologous chromosomes
(d) Loss of parts of unpaired non-homologous chromosomes

Options

A. Exchange of pairs of paired homologous chromosomes
B. Exchange of part of unpaired non-homologous chromosomes
C. Duplication of parts of pairs of paired homologous chromosomes
D. Loss of parts of unpaired non-homologous chromosomes

Answer

To solve the question regarding the formation of chiasmata, we need to understand the process of crossing over during meiosis. Here’s a step-by-step breakdown:

### Step 1: Understand Chiasmata
Chiasmata are structures that form during the process of meiosis, specifically during prophase I. They are the points where homologous chromosomes exchange genetic material.

### Step 2: Identify the Process of Crossing Over
During meiosis, homologous chromosomes pair up in a process known as synapsis. This pairing allows for the exchange of genetic material between the chromatids of homologous chromosomes, which is referred to as crossing over.

### Step 3: Recognize the Role of Homologous Chromosomes
Chiasmata are formed as a result of the exchange of genetic material between paired homologous chromosomes. This exchange leads to genetic recombination, which increases genetic diversity in gametes.

### Step 4: Evaluate the Options
Now, let’s evaluate the given options:
- (a) Exchange of pairs of paired homologous chromosomes: This is correct as it describes the process leading to chiasmata formation.
- (b) Exchange of part of unpaired non-homologous chromosomes: This is incorrect as chiasmata specifically involve homologous chromosomes.
- (c) Duplication of parts of pairs of paired homologous chromosomes: This is incorrect as duplication does not lead to chiasmata.
- (d) Loss of parts of unpaired non-homologous chromosomes: This is also incorrect as it does not relate to chiasmata formation.

### Step 5: Conclusion
The correct answer is (a) Exchange of pairs of paired homologous chromosomes.

### Final Answer:
**(a) Exchange of pairs of paired homologous chromosomes**

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