Lecture 2

Question 1

Pathogens

Answer 1

Induce illness in the host

Question 2

Four categories of pathogens

Answer 2

1. Viruses
2. Fungi
3. Parasites
4. Bacteria

Question 3

What is a virus

Answer 3

Intracellular Parasite
1. Does not have its own metabolism
2. Cannot reproduce by itself
3. “Hijacks” host cell’s machinery to reproduce
4. NOT considered living

Question 4

Composition of Viruses

Answer 4

ALL: DNA or RNA
ALL: Capsid
Some: Envelop
Variable: Additional proteins

Question 5

Virus Genetic Material

Answer 5

Genetic Material
1. DNA vs. RNA
2. single stranded vs. double stranded
3. number of genes (virus-encoded proteins)

Question 6

Viruses Morphologies: Capsid

Answer 6

Protein coat that encloses the viral nucleic acids
Multiple copies of one or a few proteins
Two general forms:
1. helical protein: rod-shaped
2. polyhedral protein: spherical

Question 7

Viruses Morphologies: Membrane Envelop

Answer 7

1. Phospholipid bilayer – glycoproteins
   Note: some viruses are enveloped; some viruses are not

Question 8

Viruses Morphologies: Complex

Answer 8

T4 bacteriophage ** NOT polyhedral or helical**
1. Polyhedral head domain
2. Hollow Tail sheath (helical)
3. Tail fibers and end plate

Question 9

Lytic Life Cycle

Answer 9

Doesn’t integrate; stays in the cytoplasm
1. Viral DNA remains and replicates independent of the HOST Genome
2. Non-enveloped: generate enzymes that degrade cell wall (rupture)
3. Enveloped: release via membrane budding

Question 10

Lysogenic Life Cycle

Answer 10

Integrates into the Nucleus
1. Does integrate its DNA into the HOST Genome
2. Replicates during periods of cell proliferation
3. De-integrates; becomes lytic as a result of cell stress

Lytic: Cell disintegration

Question 11

Virus Classification: Orders that Infects Humans

Answer 11

1. Herpesvirales: eukaryotes; dsDNA
2. Mononegavirales: animals; strand ssRNA
3. Nidovirales: vertebrates: strand ssRNA
4. Picornavirales: animals strand ssRNA