Question

RNA and DNA are chiral molecules, their chirality is due to the presence of

• A. D-sugar component
• B. L-sugar component
• C. Chiral bases
• D. Chiral phosphate ester unit

Answer 1

The Correct Option is A

To solve this problem, we need to identify the component responsible for the chirality of RNA and DNA.

1. Understanding Chirality in RNA and DNA:
RNA and DNA are both chiral molecules, meaning they lack an internal plane of symmetry and can exist in non-superimposable mirror image forms (enantiomers). The chirality in RNA and DNA arises from the structural components they are composed of, which include sugars, bases, and phosphate groups. The sugar component is the key element that imparts chirality to these molecules.

2. Identifying the Sugar Component:
Both RNA and DNA contain sugar molecules as part of their structure. The sugar in RNA is ribose, and in DNA, it is deoxyribose. These sugars are chiral because they have a central carbon (the anomeric carbon) with four different substituents, making them stereocenters. The sugars used in RNA and DNA are of the D-configuration, specifically D-ribose in RNA and D-deoxyribose in DNA, which contributes to their chirality. Therefore, the chirality of RNA and DNA is due to the presence of the D-sugar component.

3. Analyzing the Options:
Let’s evaluate each option based on the sugar's contribution to chirality in RNA and DNA:

• Option (A) "D-Sugar component" is correct because the D-sugar (ribose or deoxyribose) in RNA and DNA is responsible for their chirality.
• Option (B) "L-Sugar component" is incorrect because RNA and DNA contain D-sugar, not L-sugar.
• Option (C) "Chiral bases" is incorrect because while the bases (adenine, thymine, cytosine, guanine, and uracil) are part of the structure, they do not contribute to the overall chirality of RNA and DNA. The chirality primarily arises from the sugar component.
• Option (D) "Chiral phosphate ester unit" is incorrect because the phosphate ester unit is not the source of chirality in RNA and DNA.

Final Answer:
The correct answer is (A) "D-Sugar component."

Answer 2

The chirality of RNA and DNA is primarily due to the D-sugar component of the nucleotides that make up the DNA and RNA strands. The sugar molecules in DNA and RNA, specifically deoxyribose and ribose, are in the D-configuration, which imparts chirality to the entire molecule. The chirality of the bases and the phosphate ester group is not the primary source of chirality in these molecules.

The correct answer is (A) : D-sugar component.