AP BIOLOGY

Detailed explanation-1: -The two strands are held together by hydrogen bonds between pairs of bases: adenine pairs with thymine, and cytosine pairs with guanine.

Detailed explanation-2: -Each DNA molecule consists of two nucleotide chains wrapped around each other in a double helix and held together by hydrogen bonds. This hydrogen bonding involves only the nitrogenous bases. Each of the purine bases can hydrogen bond with one and only one of the pyrimidine bases.

Detailed explanation-3: -hydrogen. 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-4: -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. That is also the reason why the two strands of a DNA molecule can be separated more easily at sections that are densely populated by A-T base pairs.

Detailed explanation-5: -Within a molecule of DNA, pairs of bases are chemically bonded together by hydrogen bonds. These bonds hold the two strands of the molecule together. Bases pair up with each other in a consistent way, and this process is called complementary base pairing, or Watson-Crick base pairing.