BIOL 123 Lecture Notes - Lecture 30: The Double Helix, Maurice Wilkins, Cytosine
Document Summary
Nucleotides = four small subunits that dna consists: each nucleotide in dna has three parts: a phosphate group, a sugar called deoxyribose, and one of four nitrogen-containing bases, adenine (a), guanine (g), thymine (t), or cytosine (c). Chargaff"s rule the dna of any species contain equal amounts of a and t & c and g. Dna is a double helix of two nucleotide strands. All of the nucleotides within a single dna strand are oriented in the same direction. So the two ends of a dna strand differ one end has a free or unbounded sugar and the other end has a free or unbounded phosphate. Hydrogen bonds between complementary bases hold two dna strands together in a double. This forms a ladder-like structure sugar-phosphate backbones = uprights and nucleotides = rungs. Dna strands form a double helix = twisted ladder. Complementary base pairs = a-t and g-c pairs (forms each rung of the double helix ladder.
