Chapter 5 - Health And Disease - Viral Diseases/ Life Cycle of a Virus

Question 1

Name 3 viral diseases:

Answer 1

Measles, HIV, Tobacco mosaic virus

Question 2

What are the symptoms of measles?

Answer 2

~ fever

~ red skin rash

Question 3

How is measles spread?

Answer 3

Inhalation of droplets from sneezes and coughs

Question 4

What are the treatments/prevention of measles?

Answer 4

Vaccination

Question 5

What are the symptoms of HIV?

Answer 5

~ flu-like symptoms

Question 6

What does the HIV virus do? (Eg. Where does it enter, what does it develop into and why?)

Answer 6

The virus enters lymphatic system and attacks immune cells. HIV develops into AIDS when immune system can no longer deal with infections or cancer.

Question 7

How does HIV spread?

Answer 7

Through sexual contact, sharing needles, body fluids, NOT droplet infection

Question 8

How is HIV treated?

Answer 8

Antiretroviral/ antiviral drugs

Question 9

How can HIV be prevented?

Answer 9

By contraception

Question 10

What are the symptoms of tobacco mosaic virus?

Answer 10

Mosaic pattern of discolouration on leaves which affects growth by preventing photosynthesis

Question 11

How does tobacco mosaic virus spread?

Answer 11

Mechanical transmission, plant-to-plant, enters plant via wounds

Question 12

What is treatment for tobacco mosaic virus?

Answer 12

No effective treatment

Question 13

How can tobacco mosaic virus be prevented?

Answer 13

Remove infected plants as soon as possible from the garden

Question 14

Can a virus live outside the host, and what happens when they do infect one?

Answer 14

Viruses can often survive outside a host for long periods of time - when they do infect host cell(s), they replicate within cell thousands of times

Question 15

How do viruses replicate (name)? (Life cycle of a virus)

Answer 15

They do not divide and reproduce like cells (mitosis), but complete the lytic pathway

Question 16

What is the lytic pathway?

Answer 16

The process where a virus reproduces by infecting and then destroying a host cell

Question 17

What are the 4 stages of the lytic pathway?

Answer 17

1. Replicate DNA and protein coats
2. These are then assembled into new virus particles
3. This causes host cell(s) to burst
4. Other nearby cells can then be infected with the virus

Question 18

What are protein coats?

Answer 18

Proteins that surround DNA of virus

Question 19

What is the name for when the virus causes the host cell to burst?

Answer 19

Lysis

Question 20

How long does it take for the lytic pathway to happen?

Answer 20

Can be as quick as 12 hours (e.g. noravirus) or several days (e.g. Ebola)

Question 21

What do another type of virus called phages either do, and what is this called?

Answer 21

a) join their DNA to that of their host
Or
b) leave small circles of their DNA in the cytoplasm of their host cell(s)
= Lysogenic pathway
When these cells divide the DNA is copied - later in life cycle the viral DNA is copied and lytic cycle begins