its membrane. This cycle involves a virus that overtakes the host cell and its machinery to reproduce. Therefore, the virus must go through 5 stages in order to reproduce and infect the host cell: Adsorption and penetration (starting immediately) Arrest of host gene expression (starting immediately) Enzyme synthesis (starting after 5 minutes) DNA replication (starting after 10 minutes) Formation of new virus particles (starting after 12 minutes) After the life cycle is complete, the host cell bursts open and ejects the newly built viruses into the environment, destroying the host cell. T4 has a burst size of approximately 100-150 viral particles per infected host. Benzer (1955 – 1959) developed a system for studying the fine structure of the gene using bacteriophage T4 mutants defective in the rIIA and rIIB genes. The techniques employed were complementation tests and crosses to detect recombination, particularly between deletion mutations. These genetic experiments led to the finding of a unique linear order of mutational sites within the genes. This result provided strong evidence for the key idea that the gene has a linear structure equivalent to a length of DNA with many sites that can independently mutate. Adsorption and penetration Just like all other viruses, T-even phages don't just randomly attach to the surface of their host; instead they "search" and bind to receptors, specific protein structures, found on the surface of the host. These receptors vary with the phage; teichoic acid, cell wall proteins and lipopolysaccharides, flagella, and pili all can serve as receptors for the phage to bind to. In order for the T-even phage to infect its host and begin its life cycle it must enter the first process of infection, adsorption of the phage to the bacterial cell. Adsorption is a value characteristic of phage-host pair and the adsorption of the phage on host cell surface is illustrated as a 2-stage process: reversible and irreversible. It involves the phages tail structure that begins when the phages tail fibers helps bind the phage to the appropriate receptor of its host. This process is reversible. One or more of the components of the base plate mediates irreversible process of binding of the phage to a bacterium. Penetration is also a value characteristic of phage-host infection that involves the injection of the phages genetic material inside the bacterium. Penetration of nucleic acid takes place after the irreversible adsorption phase. Mechanisms involving penetration of the