Viruses

Question 1

What are viruses?

Answer 1

Obligate intracellular parasites

Question 2

What does obligate intracellular mean?

Answer 2

In order to replicate they require a live host

Question 3

Why are viruses distinguishable from other infectious agents?

Answer 3

Because they are small and are therefore filterable

Question 4

What human illnesses are viruses responsible for?

Answer 4

Influenza
Measles
Diarrhoea and vomiting
AIDS

Question 5

What plant illnesses are viruses responsible for?

Answer 5

Tobacco mosaic virus

Tomato spotted wilt virus

Question 6

What livestock illnesses are viruses responsible for?

Answer 6

Foot and mouth
SARS = severe acute respiratory syndrome
Bluetongue virus

Question 7

Where do new human viruses often originate from?

Answer 7

Viruses that are present in animals

Question 8

What are the benefits of viruses?

Answer 8

Can be used for biological control = control wild animal populations
Used for cancer treatment

Question 9

What boundaries do viruses cross?

Answer 9

Species boundaries

Question 10

What are zoonose?

Answer 10

Infectious diseases caused by bacteria, viruses and parasites that spread between animal species

Question 11

Name two common zoonose viruses?

Answer 11

Yellow fever

Dengue

Question 12

How much of our DNA is made of genetic material evolved from viruses?

Answer 12

5-8% = acquired through infection of germ cells

Question 13

How big are viruses?

Answer 13

20-300nm = too small to be seen using a light microscope

Question 14

Do viruses have a simple or complex structure?

Answer 14

Simple

Question 15

Do viruses have a big or a small genome?

Answer 15

Small

Question 16

Do viruses metabolise?

Answer 16

No

Question 17

How is genetic information encoded in viruses?

Answer 17

On one linear or circular piece of RNA or DNA (never both) surrounded by a protein coating

Question 18

How do viruses multiply in host cells?

Answer 18

Using the hosts synthesising machinery

Question 19

Name three methods of culturing animal viruses.

Answer 19

Embryonated eggs = influenza strands can be grown in chicken eggs
Cell cultures
Living animals

Question 20

How can we visualise virus replication?

Answer 20

1. Monolayer of cells poured onto a plate
2. Cells are exposed to a virus
3. Cells which have been infected with the virus can be seen

Question 21

What are cells infected with viruses called?

Answer 21

Plaques

Question 22

Why do antibiotics not work against viruses?

Answer 22

Because viruses do not metabolise

Question 23

What must drugs aimed at eliminating viruses be?

Answer 23

Specific to the virus however must no affect the host cell - must stop viral multiplication

Question 24

What is an attenuated vaccine?

Answer 24

Weakened form of the virus

Question 25

What is an inactivated vaccine?

Answer 25

A dead form of the virus

Question 26

What is a subunt vaccine?

Answer 26

Stimulates the immune system

Question 27

What is a conjugate vaccine?

Answer 27

A combination of antigen and protein to aid immune system recognition

Question 28

What is a nucleic acid vaccine?

Answer 28

Injected DNA

Question 29

How can viruses be prevented from spreading?

Answer 29

• Break transmission routes = condoms
• More people vaccinated
• Stop slaughter of infected animals
• Restricted movement of animals with viral infections
• Control vectors = eliminate mosquito’s