AP BIOLOGY

Detailed explanation-1: -A DNA molecule is made up of two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T).

Detailed explanation-2: -DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.

Detailed explanation-3: -In 1953, the race to determine how these pieces fit together in a three-dimensional structure was won by James Watson and Francis Crick at the Cavendish Laboratory in Cambridge, England. They showed that alternating deoxyribose and phosphate molecules form the twisted uprights of the DNA ladder.

Detailed explanation-4: -Concept 19: The DNA molecule is shaped like a twisted ladder. Deoxyribose and phosphate molecules form the uprights and nucleotide pair form the rungs of the DNA ladder.