DNA cloning and mutagenesis are widespread tools in biology. Understanding the structural/functional relationship of the proteins is of great interest, with the aim to clarify the relationships often the researchers used the mutagenic approach. In the last 20 years, several mutagenesis systems have been developed, analyzing them it’s possible to observe the “evolution” of mutagenesis. Here, a short description and differences among three methods widely used of mutagenesis are shown. This method was designed to increase the rate of mutagenesis respect to the method developed by Smith. The main feature of the method is obtaining the vector containing the gene of interest with uracil in place of thymidine. The single strand DNA template is obtained by transforming the vector, having the origin of replication of the M13 phage, into an E. coli dut- ung- strain. The infection of recombinant colonies with M13 phage determines the production of viral particles constituted by single strand uracil-containing DNA vector.