True or False: Asymmetrical spacing of the DNA backbones generates major and minor grooves.

• A. Not applicable
• B. False
• C. Both
• D. True

Answer: (D)

The spacing of the two sugar-phosphate backbones around the DNA double helix is not the same on all sides, so as the strands twist, two distinct spaces appear: a wide major groove and a narrow minor groove. This unequal spacing is what creates the two grooves, not a single uniform surface. The major groove is large enough to let proteins and other molecules “read” the exposed edges of the base pairs, facilitating sequence-specific interactions, while the minor groove presents a different, smaller surface with its own pattern of contacts. Because the asymmetrical arrangement of the backbones leads directly to these two grooves, the statement is true.