Читать книгу Essential Endocrinology and Diabetes - Richard I. G. Holt - Страница 35

 A molecule of deoxyribose (a five‐carbon sugar) is linked covalently to one of two types of nitrogenous bases:Purine – adenine (A) or guanine (G)Pyrimidine – thymine (T) or cytosine (C)The base plus the sugar is termed a ‘nucleoside’, e.g. adenosine

 The addition of a phosphate group to a nucleoside creates a nucleotide. E.g. adenosine mono‐, di‐ or tri‐phosphate (according to how many phosphate groups have been added)

 Phosphodiester bonds polymerize the nucleotides into a single strand of DNA

 Two strands, running in opposite directions, 5 prime (5′; upstream) to 3′ (downstream) assemble as a double helix:Hydrogen bonds form between the strands, between the base pairs A–T and G–C

 ∼3 billion base pairs comprise the human genome