The functional unit of DNA molecule that codes for a particular gene product is

Options

A. Cistron
B. Exon
C. Intron
D. Gene

Answer

To answer the question "The functional unit of DNA molecule that codes for a particular gene product is", we will analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Options**:
- We have four options: cystron, axon, intron, and gene. We need to identify which one correctly describes the functional unit of DNA that codes for a gene product.

2. **Evaluating the First Option - Cystron**:
- A cystron is defined as a functional unit of DNA that encodes for a particular protein. It is a term often used to describe a segment of DNA that can produce a polypeptide chain. Therefore, this option is a strong candidate.

3. **Evaluating the Second Option - Axon**:
- An axon refers to the coding sequences of mRNA. While axons are important in the context of gene expression, they are not the functional unit of DNA itself. Instead, they are derived from the coding regions of a gene after transcription. Thus, this option is incorrect.

4. **Evaluating the Third Option - Intron**:
- Introns are non-coding regions found within a gene. They are transcribed into RNA but are removed during the splicing process before the mRNA is translated into protein. Since introns do not code for any gene product, this option is also incorrect.

5. **Evaluating the Fourth Option - Gene**:
- A gene is a broader term that refers to a segment of DNA that contains the necessary information to produce a functional product, usually a protein. While it is a functional unit of heredity, it is not as specific as the term "cystron" in the context of coding for a particular product.

6. **Conclusion**:
- Based on the analysis, the correct answer is **cystron**, as it specifically denotes the functional unit of DNA that encodes for a particular gene product.

### Final Answer:
The functional unit of DNA molecule that codes for a particular gene product is **cystron**.

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