The presence or absence of hydroxy group on which carbon atom of sugar differentiates `RNA` and `DNA`.

Options

A. `1^(st)`
B. `2^(nd)`
C. `3^(rd)`
D. `4^(th)`

Answer

To differentiate between RNA and DNA based on the presence or absence of a hydroxy group on a specific carbon atom of sugar, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of RNA and DNA:**
- Both RNA (Ribonucleic Acid) and DNA (Deoxyribonucleic Acid) are nucleic acids that contain sugar molecules as part of their structure.

2. **Identify the Sugar Types:**
- RNA contains ribose sugar.
- DNA contains deoxyribose sugar.

3. **Analyze the Sugar Structures:**
- Ribose (the sugar in RNA) has the following structure:
- C1: OH
- C2: OH
- C3: OH
- C4: H
- C5: H
- Deoxyribose (the sugar in DNA) has the following structure:
- C1: OH
- C2: H (no OH group)
- C3: OH
- C4: H
- C5: H

4. **Identify the Key Difference:**
- The key difference between ribose and deoxyribose is at the second carbon (C2):
- In ribose (RNA), C2 has a hydroxy group (OH).
- In deoxyribose (DNA), C2 does not have a hydroxy group (it has only H).

5. **Conclusion:**
- The presence of the hydroxy group on the second carbon atom differentiates RNA from DNA.

### Final Answer:
The presence or absence of the hydroxy group on the **second carbon atom** of sugar differentiates RNA and DNA.

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