Explain lysogenic cycle of a phage.

Explanation

1. In the lysogenic cycle, the phage DNA gets integrated into the DNA of the host cell and gets multiplied along with nucleic acid of the host. No independent viral particle is formed.
2. As soon as the phage injects its linear DNA into the host cell it becomes circular and integrates into the bacterial chromosome by recombination. The integrated phage DNA is now called prophage.
3. The activity of the prophage gene is repressed by two repressor proteins which are synthesized by phage genes. This checks the synthesis of new phages within the host cell.
4. However, each time the bacterial cell divides, the prophage multiplies along with the bacterial chromosome.
5. On exposure to UV radiation and chemicals the excision of phage DNA may occur and results in lytic cycle.