The diagram at the top of the page is a virus that commonly infects bacteria cells. This virus is usually referred to as a bacteriophage . There are specific sites called receptor sites that the viruses attach to on the host cell's surface. Virus attaches itself to the cell. Enzymes weaken the cell wall and nucleic acid is injected into the cell, leaving the empty caspid outside the cell.
Many viruses actually enter the host cell intact.
Viral DNA takes control of cell activity. Enzymes disintegrate the cell in a process called lysis , releasing the new viruses. The virus attaches itself and injects its DNA into the cell. The viral DNA attaches itself to the host DNA, becoming a new set of cell genes called a prophage . When the host cell divides, this new gene is replicated and passed to new cells, causing no harm to the cell.