DNA exists in a double-stranded form whereas RNA is mainly a single stranded molecule. What is the likely reason for DNA being double stranded?

Options

A. RNA strands cannot form base pairs.
B. Double stranded DNA is a more stable structure.
C. DNA cannot exist in the single stranded form
D. It is easier to replicate double stranded DNA than single stranded RNA.

Answer

**Step-by-Step Solution:**

1. **Understanding the Structure of DNA and RNA:**
- DNA (Deoxyribonucleic Acid) is composed of two strands that form a double helix structure.
- RNA (Ribonucleic Acid) is primarily single-stranded.

2. **Analyzing the Stability of DNA:**
- The double-stranded structure of DNA provides greater stability compared to RNA.
- This stability is crucial for the long-term storage of genetic information.

3. **Examining the Sugar Components:**
- The sugar in DNA is deoxyribose, which has one hydroxyl group (OH) less than ribose, the sugar found in RNA.
- In DNA, the sugar has one hydrogen (H) at the 2' position, making it less reactive and more stable.

4. **Comparing Reactivity:**
- The presence of two hydroxyl groups in RNA (at the 2' and 3' positions) makes it more reactive and less stable than DNA.
- This increased reactivity contributes to RNA's tendency to be single-stranded.

5. **Conclusion:**
- The primary reason for DNA being double-stranded is its stability due to the structure of its sugar (deoxyribose) and the absence of the additional hydroxyl group present in RNA.

**Final Answer:**
The likely reason for DNA being double-stranded is that a double-stranded DNA is a more stable structure compared to single-stranded RNA, primarily due to the presence of deoxyribose sugar in DNA, which has one less hydroxyl group than ribose sugar in RNA.

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