AP BIOLOGY

Detailed explanation-1: -The Adenine-Thymine base pair is held together by 2 hydrogen bonds while the Guanine-Cytosine base pair is held together by 3 hydrogen bonds.

Detailed explanation-2: -Covalent bonds occur within each linear strand and strongly bond the bases, sugars, and phosphate groups (both within each component and between components). Hydrogen bonds occur between the two strands and involve a base from one strand with a base from the second in complementary pairing.

Detailed explanation-3: -Reason: Adenine specifically forms hydrogen bonds with guanine whereas cytosine forms hydrogen bonds with thymine.

Detailed explanation-4: -Hydrogen bonds are a special type of dipole-dipole forces. In hydrogen bonding, the dipole-dipole attraction occurs between hydrogen and a highly electronegative atom(O, F, Cl, etc). Hydrogen bonds are much stronger than a general dipole-dipole force.