What type of bond forms when a slightly positive hydrogen atom is attracted to a slightly negative atom in polar molecules, helping hold DNA together?

• A. Hydrogen bond
• B. Ionic bond
• C. Covalent bond
• D. Base pairs

Answer: (A)

Hydrogen bonds are the noncovalent attractions that form when a hydrogen atom bonded to a highly electronegative atom (like nitrogen or oxygen) carries a partial positive charge and is attracted to another electronegative atom with lone pairs carrying a partial negative charge. This polarity creates a directional, relatively weak bond that’s enough to hold DNA strands together yet allows them to separate during replication. In DNA, this type of bonding underpins base pairing (A–T and G–C), giving the double helix its stability without making the strands permanently fuse. This is distinct from ionic bonds, which rely on full charges from electron transfer, or covalent bonds, which involve shared electrons to form a molecule. Base pairs refer to the paired bases themselves, not the type of bond.