Question

Which of the following events occurs in the animal virus life cycle, but NOT in the bacteriophage life cycle? Check all that apply.

		Formation of a pro-virus
		Release by budding
		Uncoating
		Use of host cell ribosomes to synthesize viral proteins
		Biosynthesis
		Assembly of new virus particles
		Viral capsid enters into the host cell
		Lysis

Answer 1

Answer : Formation of a pro-virus

Release by budding

Uncoating

Viral capsid enters the host cell

Although bacteriophages and animal cell viruses show similar stages of infection like attachment penetration, biosynthesis, maturation and release, there exists some difference in bacterial and animal cell viruses with respect to the mechanism of penetration, nucleic acid biosymthesis and release of virus particles. Bacteriophages upon attachment to the host cell, injects the nucleic acid into the host cell leaving behind the capsid and other components. Animal viruses enters the host cell by endocytosis in which the cell membrane surrounds and engulfs the entire cell. Some enveloped viruses enters the host cell by membrane fusion in which the viral envelope fuses with the cellular membrane. In both cases the viral capsid enters the host cell, which is then degraded releasing the virus nucleic acid by a process known as uncoating.

The release of bacteriophages occurs by the lysis of bacterial cells. Animal viruses may releases by either lysis or budding. Non enveloped viruses are release by lysis resulting in the death of the infected host cell, whereas enveloped viruses are released by budding through the membrane without directly killing the host cell.

Some viral genomes such as in the case of HIV, can integrate into the host chromosome and replicates along with the host genome. This viral genome is called as provirus - a term specific for viruses that infect animal cells. Like wise when a bacteriophage integrates with the host genome and replicates with it ( in lysogenic cycle ), the viral genome is called a prophage