Basic Genetics: A Brief Partly Guided Tour of DNA
The large macromolecules, the nucleic acids DNA and RNA, serve many functions. The vital structural property of both molecules is that they are modular, each is a string of concatenated nucleotide bases, of which there are four basic types: adenine (A), cytosine (C), guanine (G), and thymine (T) (or in a modified form as uracil (U) in RNA). These are linked by a phosphate-sugar backbone. Each of the two purines (G and A) easily forms a chemical bond with one of the two pyrimadines (C and T/U): C pairs with G and A with T.This complementary base pairing allows the molecule to take on higher-order three-dimensional structure, and these basic properties are used both by nature and by experimenters to manipulate DNA and RNA, including the important function of replication in which a DNA molecule is copied and passed down from one cell generation to the next. Indeed, much of life and of our research methods to understand life is based on complementary base pairing.
The most important characteristics of both molecules are that (1) the length of the concatenated string of nucleotides is chemically arbitrary and (2) the sequence of successive nucleotides can be arranged in any order. Clearly, both molecules are modular in nature and the subunits are variations on a basic chemical theme—and this is how and why it works.
Genetics and the Logic of Evolution, by Kenneth M. Weiss and Anne V. Buchanan. ISBN 0-471-23805-8 Copyright © 2004 John Wiley & Sons, Inc.
Building Blocks of Life Sugar Phosphate Backbone of DNA
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