Chapter 5 Viruses

Question 1

What is a virus

Answer 1

Obligate intracellular parasite - only able to reproduce within cells
–not a cell or living organism

Question 2

What are the viral capsid and genome composed of?

Answer 2

protein and nucleic acid respectively (DNA or RNA)

Question 3

Bacteriophage Life Style

Answer 3

1) Attachment/Absorption - binding to the exterior of a bacterial cell
2) Penetration/Eclipse - capsid remains on outer surface of the bacterium while the genome disappears into the cell rempving infectious virus from the media
3) enter lysogenic or lytic cycle

Question 4

Lytic Cycle

Answer 4

1) Attachment of phage to E. Coli and injection of phage chromosome
2) Breakdown of bacterial chromosome by phage-specfic enzyme
3) Replication of phage chromosome using bacterial materials and phage enzymes
4) Expression of phage genes to produce phage structural components
5) Assembly progeny phage particles
6) Release of progeny phage by lysis of bacterial wall

Question 5

Lytic Cycle advantage and disadvantages

Answer 5

Pro: increase rapidly
Con: kill host right away so it needs to keep spreading

Question 6

Lysogenic Cycle

Answer 6

1) The Phage binds to the bacterium
2) The phage DNA enters the host cell
3) The Phage DNA integrates and becomes non-infective prophage
4) Chromosome with integrated prophage replicates
5) In rare cases, the prophage may separate and the cell will be induced to lyse