RNA is not a double helix.

RNA is not a double helix.

• A. Not a double helix
• B. Forms a double helix
• C. Contains deoxyribose
• D. Pairs with thymine

Answer: (A)

RNA is typically a single strand, so it is not a double helix. DNA maintains a long, up-and-down double-stranded structure because its two antiparallel strands pair with complementary bases, forming a stable helix. RNA differs in two key ways: it uses ribose sugar (with a reactive 2'‑OH) instead of deoxyribose, and it contains uracil instead of thymine. Because RNA is usually single-stranded, it doesn’t adopt the uniform double-helix shape of DNA; it can fold back on itself to create local double-stranded regions or various shapes, but the overall structure isn’t a classic DNA-like helix. So the statement that RNA is not a double helix is accurate.

RNA is typically a single strand, so it is not a double helix. DNA maintains a long, up-and-down double-stranded structure because its two antiparallel strands pair with complementary bases, forming a stable helix. RNA differs in two key ways: it uses ribose sugar (with a reactive 2'‑OH) instead of deoxyribose, and it contains uracil instead of thymine. Because RNA is usually single-stranded, it doesn’t adopt the uniform double-helix shape of DNA; it can fold back on itself to create local double-stranded regions or various shapes, but the overall structure isn’t a classic DNA-like helix. So the statement that RNA is not a double helix is accurate.