In DNA, what intermolecular force primarily holds complementary base pairs together (A with T, and G with C)?

• A. Metallic bonding within the base pair
• B. Ionic bonding between the phosphate groups and the bases
• C. Covalent bonding between the two bases in each pair
• D. Hydrogen bonding between polar functional groups on the bases

Answer: (D)

Verified step by step guidance

1. Identify the types of intermolecular forces that can occur between molecules: these include hydrogen bonding, ionic bonding, covalent bonding, metallic bonding, and van der Waals forces.
2. Understand the structure of DNA base pairs: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). These pairs are held together by specific interactions between polar functional groups on the bases.
3. Recall that covalent bonds are strong bonds within molecules, not typically responsible for holding separate molecules or bases together in DNA base pairing.
4. Recognize that metallic bonding occurs between metal atoms and is not relevant to organic molecules like DNA bases.
5. Conclude that the primary intermolecular force holding complementary base pairs together in DNA is hydrogen bonding, which occurs between polar functional groups (such as -NH and =O groups) on the bases.