Introduction

Abstract

The sequence of nucleotides in DNA dictates the sequence of amino acids in the proteins of a cell and hence the form and function of a cell. This is the so-called central dogma of molecular biology. Because of the sequence complementarity of the strands of the DNA duplex, this sequence can be transferred to daughter cells following semiconservative replication and cell division. The replication of DNA occurs with high fidelity and, in general, only one round of replication occurs per cell cycle. Any errors that arise are corrected and any damage to DNA is usually quickly repaired. The DNA in the cell is neither naked, nor is it stretched out in the familiar B form revealed by fiber X-ray diffraction studies. Rather it is associated with proteins and RNA in such a way that it can be packed into the cell and yet transcribed and replicated in an orderly manner.