Which of the Following Stabilizes the DNA Double-Helix Structure

Question

Which of the following stabilizes the DNA double-helix structure?
A)The sugar-phosphate backbones are oriented in parallel directions.
B)Bases stack together through hydrophobic interactions and van der Waals forces.
C)The glycosidic bonds holding paired bases are directly across the helix from one another.
D)Appropriate base pairing builds a polymer whose external dimensions are not consistent.

Accepted Answer

The stacking of the aromatic nitrogenous bases through hydrophobic interactions and van der Waals forces helps to stabilize the DNA double-helix structure. This stacking also provides protection to the interior of the helix from water molecules and other foreign substances that could disrupt the hydrogen bonding between the base pairs. The parallel orientation of the sugar-phosphate backbone and the consistent spacing between base pairs also contribute to stabilizing the helix, but these factors are not as critical as the stacking of the bases. The glycosidic bonds holding paired bases across from each other also contribute to the stability of the helix but more by dictating the specific sequence of base pairs rather than through direct stabilization of the helix structure. Inappropriate base pairing, such as pairing of non-complementary base pairs, would actually destabilize the helix rather than stabilize it. Therefore, D is an incorrect option.