Microbiology Exam 1

Question 1

Progressive escape hypothesis (viruses)

Answer 1

viruses arose from genetic elements that gained the ability to move between cells

Question 2

Regressive or reduction hypothesis

Answer 2

viruses are remnants of cellular organisms

Question 3

virus first hypothesis

Answer 3

coevolved with their current cellular hosts

Question 4

What are obligatory intracellular parasites composed of?

Answer 4

nucleic acid genome
protein coat
some enclosed by an envelope
some viruses have spikes

Question 5

Explain host range

Answer 5

determined by the specific host attachment sites and cellular factors

Question 6

explain tissue tropism

Answer 6

the fact that viruses can only infect specific types of cells

Question 7

explain capsid structure

Answer 7

how virus capsid can be constructed using multiple copies of just two protein molecules in the cowpea mosaic virus

Question 8

characteristics of spherical virus

Answer 8

includes influenza virus
spherical and contains many glycoprotein spikes on outside
8 single stranded RNA molecules each wrapped in separate capsid
others may include single capsid the encloses genetic material

Question 9

characteristics of icosahedral virus

Answer 9

includes adenovirus
icosahedral shape
no envelope
capsid contains glycoprotein spikes on each vertex
one DsDNA molecule inside capsid

Question 10

characteristics of helical virus

Answer 10

includes tobacco mosaic virus
helically shaped rod w/ no envelope
one ssRNA molecule

Question 11

characteristics of complex virus

Answer 11

includes bacteriophages
head and tail and lack envelope
head contains dsDNA
tail consists of sheath and protein fibers which assist in docking to host cell
any non-symmetrical virus is considered complex

Question 12

In what conditions can animal cells be grown?

Answer 12

living animals
embryonated eggs
cell culture

Question 13

where are plant viruses grown?

Answer 13

grown directly on plants or plant tissue culture.

Question 14

Where must viruses grow?

Answer 14

must grow in living cells
specific for what cell-type they prefer

Question 15

How do bacteriophages grow?

Answer 15

form plaques on a lawn of bacteria

Question 16

Explain process of animal and plant virus grown in cell culture.

Answer 16

1. a tissue is treated with enzymes to separate the cells
2. cells are suspended in culture medium
3. normal or primary cells grow in monolayer across the glass or plastic container. transformed cells or continuous cell cultures don’t grow in monolayer.

Question 17

Explain cytopathic effects viral identification

Answer 17

alters shape
detachment of substrate
lysis
membrane fusion
altered membrane permeability
inclusion bodies
apoptosis