The first two chapters covered many important aspects of genes, such as how they function in inheritance, how they code for protein (in general terms) and their chemical nature. All this was learned without having a single gene purified. A full understanding of a gene, or the entire set of genes in a genome, requires that they be isolated and then studied intensively. Once a gene is “in hand”, in principal one can determine both its biochemical structures and its function(s) in an organism. One of the goals of biochemistry and molecular genetics is to assign particular functions to individual or composite structures. This chapter covers some of the techniques commonly used to isolate genes and illustrates some of the analyses that can be done on isolated genes.