Chapter 5 - Health And Disease - Viral Diseases/ Life Cycle of a Virus Flashcards
Name 3 viral diseases:
Measles, HIV, Tobacco mosaic virus
What are the symptoms of measles?
~ fever
~ red skin rash
How is measles spread?
Inhalation of droplets from sneezes and coughs
What are the treatments/prevention of measles?
Vaccination
What are the symptoms of HIV?
~ flu-like symptoms
What does the HIV virus do? (Eg. Where does it enter, what does it develop into and why?)
The virus enters lymphatic system and attacks immune cells. HIV develops into AIDS when immune system can no longer deal with infections or cancer.
How does HIV spread?
Through sexual contact, sharing needles, body fluids, NOT droplet infection
How is HIV treated?
Antiretroviral/ antiviral drugs
How can HIV be prevented?
By contraception
What are the symptoms of tobacco mosaic virus?
Mosaic pattern of discolouration on leaves which affects growth by preventing photosynthesis
How does tobacco mosaic virus spread?
Mechanical transmission, plant-to-plant, enters plant via wounds
What is treatment for tobacco mosaic virus?
No effective treatment
How can tobacco mosaic virus be prevented?
Remove infected plants as soon as possible from the garden
Can a virus live outside the host, and what happens when they do infect one?
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
How do viruses replicate (name)? (Life cycle of a virus)
They do not divide and reproduce like cells (mitosis), but complete the lytic pathway
What is the lytic pathway?
The process where a virus reproduces by infecting and then destroying a host cell
What are the 4 stages of the lytic pathway?
- Replicate DNA and protein coats
- These are then assembled into new virus particles
- This causes host cell(s) to burst
- Other nearby cells can then be infected with the virus
What are protein coats?
Proteins that surround DNA of virus
What is the name for when the virus causes the host cell to burst?
Lysis
How long does it take for the lytic pathway to happen?
Can be as quick as 12 hours (e.g. noravirus) or several days (e.g. Ebola)
What do another type of virus called phages either do, and what is this called?
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
