2.2 Viruses Flashcards
(18 cards)
Virus
Viruses are small, non-living particles
Consist of genetic material (DNA or RNA) surrounded by a protein capsid
They have no cytoplasm and are very, very tiny (less than 0.1 micrometer)
Cannot grow and reproduce on their own
All are infectious, they enter a cell, take control and eventually the cell makes copies of the virus
The importance of Viruses (what is it responsible for)
Responsible for many human diseases – common cold, chicken pox, AIDS, rabies, influenza
play a role in causing cancer (hepatitis C and liver cancer, HPV and cervical cancer)
Plant viruses destroy millions of tonnes of crops every year, including beets, tobacco, tomatoes, and sugar cane
Epidemic
A breakout of a disease (of any origin) that is kept to a localised area
Pandemic
An epidemic that has spread across multiple geographical areas
How can a virus cause population decline
Viruses are abundant in all ecosystems
They affect all types of organisms
Viruses can spread easily among members of the same species, causing populations to decline
Classification of a virus
They are classified into orders, families, genera and species (approx. 4000) based on size, shape, and type of genetic material
Why are viruses considered to be non-living?
because they cannot reproduce without a host cell
A bacteriophage
is a virus that infects bacterial cells (“bacteria eater”)
Lysis
occurs when the host cell ruptures
Lysogeny
is when the viral DNA can stay in a dormant state
Transduction
when a little bit of bacterial DNA attaches to viral DNA and it can be inserted into a different bacterial cell
Vaccines
Vaccines are mixtures containing weakened forms or parts of a virus
How vaccines work
An immune response is triggered, without causing an infection
The body now has a chemical “memory” that allows the immune system to react quickly if exposed to the real virus
Where can viruses be used?
Viruses can be used in genetic engineering and in gene therapy —the treatment of diseases using genes
How can viruses can deliver drugs or genes to targeted cells?
They place drugs inside virus capsules or replace the viral DNA with DNA they want to insert into a host cell.
Viroid
A very small infectious piece of RNA responsible for some serious diseases in plants
Possibly a precursor to life on Earth
No envelope or capsid for protection
What is prion short for
Short for “proteinaceous infectious particle”
what is a prion
An abnormally shaped infectious protein responsible for some brain diseases of mammals, including humans (mad cow disease in the late 1980’s)
