DNA Structure, Replication, Transcription and Translation Practice Test

Stability and information-carrying roles come from the chemistry of the sugar in the backbone and the overall structure. DNA is a stable, double-stranded molecule built from deoxyribose and thymine. The absence of a 2' hydroxyl group on deoxyribose makes the backbone less prone to hydrolysis, and the double-stranded form provides protection and fidelity during replication and repair. RNA, on the other hand, is typically single-stranded and uses ribose with a 2'-hydroxyl and uracil instead of thymine. The 2'-OH makes RNA's backbone more chemically reactive and more susceptible to hydrolysis, so RNA is generally less stable and suited for short-lived, transient roles in the cell—such as carrying genetic information briefly (mRNA) and acting as functional or regulatory molecules (tRNA, rRNA, various RNAs). This combination of structural features and base composition explains why DNA is stable and long-lasting, while RNA is more ephemeral and versatile in function.