The presence or absence of a hydroxyl group on which a carbon atom of sugar differentiates RNA and DNA

2nd

The correct answer is option 2. 2nd.

Let us dive into the structural differences between RNA and DNA and the significance of the hydroxyl group on the 2' carbon atom of the sugar.

Structural Differences:

1. Sugar Component:

RNA (Ribonucleic Acid): The sugar in RNA is ribose. Ribose is a five-carbon sugar with hydroxyl groups (-OH) attached to both the 2' and 3' carbon atoms.

DNA (Deoxyribonucleic Acid): The sugar in DNA is deoxyribose. Deoxyribose is similar to ribose but lacks the hydroxyl group at the 2' carbon atom. Instead, it has a hydrogen atom (H) at this position, hence the name "deoxy" (meaning "lacking oxygen").

Significance of the 2' Hydroxyl Group:

Chemical Stability: The absence of the 2' hydroxyl group in DNA makes it more chemically stable than RNA. The hydroxyl group in RNA is reactive and can participate in hydrolysis reactions, leading to the breakdown of the RNA strand. This is one reason why DNA is better suited for long-term storage of genetic information, while RNA is more suitable for temporary functions such as protein synthesis.

Structural Implications: The presence of the 2' hydroxyl group in RNA introduces steric hindrance and affects the secondary structure of RNA. RNA is often single-stranded and can form complex three-dimensional shapes through intramolecular base pairing. These structures are crucial for the diverse functions of RNA molecules, including catalysis (as in ribozymes) and regulation (as in riboswitches).

DNA, lacking the 2' hydroxyl group, typically forms a more stable double helix with a consistent structure. This stability is essential for the reliable storage and transmission of genetic information.

Functionality: The 2' hydroxyl group in RNA is critical for its function in the cell. For example, in ribosomal RNA (rRNA) and transfer RNA (tRNA), the 2' hydroxyl group participates in catalytic activities and the proper positioning of the RNA molecules during protein synthesis.

DNA’s simpler structure without the 2' hydroxyl group allows it to form long, stable double-stranded helices, making it ideal for its role in storing genetic information over the long term.

The key structural difference between RNA and DNA lies in the presence of a hydroxyl group on the 2' carbon of the ribose sugar in RNA, which is absent in DNA (replaced by a hydrogen atom). This small chemical difference has profound effects on the stability, structure, and function of these molecules. RNA’s 2' hydroxyl group makes it more reactive and versatile for various cellular functions, while DNA’s lack of this group contributes to its stability and suitability for long-term genetic information storage.