Biology 1001A Lecture Notes - The Double Helix, Dna Replication, Guanine
Document Summary
Carbohydrates, lipids, proteins and nucleic acids are the four main types of biological macromolecules. The structure of carbohydrates and lipids is repetitive and so are not likely to carry information. The structure of proteins and nucleic acids are built of various combinations of amino acids and nucleotides making them likely for carrying information. Dna contains four different nucleotides. (adenine-guanine, thymine-cytosine) Each nucleotide consists of five carbon sugar deoxyribose, a phosphate group and one of the four nitrogenous bases. Adenine and guanine are purines and thymine and cytosine are pyrimidine. The double helix model of two sugar-phosphate backbones are separated from each other by a regular distance. Watson and crick proposed semi conservative replication the process of dna replication in which the two parental strands separate and each serves as a template for the synthesis of new progeny double stranded dna molecules. Dna polymerase can add a nucleotide only to the 3" end of an existing nucleotide chain.