How does the structure of RNA differ from DNA?

The correct assertion regarding the structural differences between RNA and DNA highlights that RNA is typically single-stranded and contains uracil instead of thymine. This distinction is fundamental to understanding the roles these nucleic acids play in biological systems.

RNA's single-stranded nature allows it to fold into various shapes, playing critical roles in processes such as translation and transcription. This structural flexibility is essential for RNA's functions, including serving as a messenger (mRNA), adaptor (tRNA), and structural or catalytic units (rRNA).

Moreover, the presence of uracil in RNA, instead of thymine, is significant as it affects base pairing during processes such as transcription. In RNA, uracil pairs with adenine, similar to how thymine does in DNA, but this slight difference in structure avoids the redundancy and stability provided by thymine’s methyl group in DNA, reflecting the more transient and versatile nature of RNA.

Overall, this understanding of RNA's unique structure underlies its varied functions in the cell, contrasting sharply with the more stable, double-stranded structure of DNA, which is designed to securely store genetic information.