PHYLOGENY ESTIMATION USING MAXIMUM LIKELIHOOD
By George Shanahan
DNA: The Information for Reconstructing Phylogenetic Trees
DNA is the basic hereditary material in all cells and contains all the information necessary to make proteins. DNA is a linear polymer that is made up of nucleotide units. The nucleotide unit consists of a nitrogen containing base, a deoxyribose sugar, and a phosphate. There are four types of bases: adenine (A), thymine (T), guanine (G), and cytosine (C). Each base is connected to a sugar via a ß glycosyl linkage. The nucleotide units are connected via the O3' and O5' carbon atoms forming phosphodiester linkages. This linkage between the hydroxyl groups of the deoxyribose sugar and the phosphate groups form the DNA backbone.
adenine thymine guanine cytosine
In normal DNA, the bases form pairs: A to T and G to C. This is called complementarity. Two complementary chains that are arranged in an anti-parallel manner form a duplex of DNA. The A-T and G-C base pairs are the same length, and occupy the same space
within a DNA double helix, creating a uniform diameter. DNA is normally a double stranded macromolecule, consisting of two polynucleotide chains held together. Also known as a double helix.