NCERT · Class 12 · Chemistry · BiomoleculesDifferentiate between DNA and RNA in terms of their sugar components, nitrogenous bases, and structural conformation.

DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) are fundamental nucleic acids responsible for the storage and expression of genetic information. They differ in several key structural aspects:

1. Sugar Component: DNA contains $\beta$-D-2-deoxyribose sugar, which lacks an oxygen atom at the C-2 position. On the other hand, RNA contains $\beta$-D-ribose sugar, which possesses a hydroxyl group ($-\text{OH}$) at the C-2 position.

2. Nitrogenous Bases: Both DNA and RNA contain purine bases (Adenine and Guanine) and pyrimidine bases. However, their pyrimidine composition differs: DNA contains Cytosine and Thymine, whereas RNA contains Cytosine and Uracil (Thymine is replaced by Uracil in RNA).

3. Structural Conformation: DNA predominantly exists as a stable double-stranded helical structure where two polynucleotide chains run anti-parallel and coil around a central axis. RNA typically exists as a single-stranded molecule, which can sometimes fold back on itself to form complex hairpin loops and tertiary structures. \nThese structural differences enable DNA to act as a permanent, highly secure archive for genetic instructions, while RNA plays active roles in protein synthesis and translation processes.