Antiparallel DNA strands are held together by _____ _____ between the bases oriented toward the center.

Antiparallel DNA strands are held together by _____ _____ between the bases oriented toward the center.

• A. Covalent bonds
• B. Ionic bonds
• C. Disulfide bonds
• D. Hydrogen bonds

Answer: (D)

Antiparallel DNA strands are held together by hydrogen bonds between the bases that face each other in the center of the helix. The sugar-phosphate backbones stay connected by covalent phosphodiester bonds along the outside, but the base pairs themselves are stabilized by hydrogen bonding—A pairs with T via two hydrogen bonds and G pairs with C via three. These hydrogen bonds are strong enough to keep the double helix intact yet weak enough to allow strand separation during replication and transcription. Ionic interactions or disulfide bonds aren’t the primary forces holding the base pairs together, so the key connection between the bases toward the center is hydrogen bonding.

Antiparallel DNA strands are held together by hydrogen bonds between the bases that face each other in the center of the helix. The sugar-phosphate backbones stay connected by covalent phosphodiester bonds along the outside, but the base pairs themselves are stabilized by hydrogen bonding—A pairs with T via two hydrogen bonds and G pairs with C via three. These hydrogen bonds are strong enough to keep the double helix intact yet weak enough to allow strand separation during replication and transcription. Ionic interactions or disulfide bonds aren’t the primary forces holding the base pairs together, so the key connection between the bases toward the center is hydrogen bonding.