Chapter 2 - Nucleic Acid-Based Cellular Activities

Abstract

Commonly, the flow of genetic information in a cell can be demonstrated by the example of a bacterium in which only a single circular chromosome is present; the genetic information contained therein can be used within that cell and also passed between cells. Many cellular activities, including DNA replication, recombination, and gene expression, are nucleic acid-based activities. Before cells divide, for example, they must make a complete and faithful copy of the DNA in their chromosomes. This process of copying DNA is called replication. During replication, each strand of DNA double helices is copied to make a new strand, thus producing two new daughter DNA double helices. Thus, DNA replication demonstrates the flow of genetic information that can be passed from one generation to the next. During DNA replication, some errors may be introduced; therefore, DNA repair exists to ensure the fidelity of genetic information which is to be passed to the next generation. One mechanism of DNA damage repair relies on recombination, which makes it possible to transfer the genetic information between cells of the same generation. This is because it involves the direct exchange of genetic material through the double-strand DNA breaks. Gene expression is used within a cell to produce the proteins needed for the cell to function. We will discuss DNA replication, DNA repair, and recombination in this chapter and gene expression in Chapters 3 and 4.