Biology, Eighth Edition (Raven)

Chapter 28: Prokaryotes

Life Cycle of T2 Phage

Why are some viruses called phage? A phage is a virus that attacks bacteria. Phages are among the best known of viruses because of the ease of studying bacterial systems. Many phages are among the most structurally complex viruses known. The T2 phage is typical one common group of phages. The body of the virus, called a capsid, is a complex structure with a head containing DNA and a tail apparatus that attaches to receptors on the surface of the bacterial host. T2 and all the other T phages that attack E. coli have a lytic life cycle. If they are successful in infecting a cell, the cell is invariably destroyed. Other phages have lysogenic life cycles that do not necessarily harm the host cell.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	What part of the phage enters the bacterial cell following infection?

		A)	DNA
		B)	RNA
		C)	protein coat
		D)	the entire phage
		E)	no part

2.	The protein coat that surrounds the genetic material of the T2 phage is termed the

		A)	capsid.
		B)	envelope.
		C)	nucleoid.
		D)	membrane.
		E)	cell wall.

3.	Mature T2 phage particles are released

		A)	after lysis of the bacterial host cell.
		B)	by budding through the bacterial cell membrane.
		C)	by budding through the bacterial nuclear membrane.
		D)	by diffusion through the bacterial cell membrane.
		E)	by phagocytosis of the bacterial host cell.

4.	Phage T2 infection of a bacterial cell is accompanied by degradation of host cell DNA.

		A)	True
		B)	False

5.	The term phage is an abbreviation of the word bacteriophage.

		A)	True
		B)	False