Viruses, viroids and prions Flashcards
Learn about Poh's many many sexual diseases.
What is a virus?
One or more nucleic acid molecules within a coat of protein.
What are some characteristics of viruses?
Can replicate and evolve
Do not grow
Have no ribosomes
Contain DNA or RNA, not both
Are insensitive to changes in their environment
Can only reproduce inside a living cell: obligate parasite
Affect organisms from all domains of life
Very small
What does it mean if a virus is enveloped?
Surrounded by a lipid membrane acquired from the cell or nuclear membrane of an infected cell: this membrane is its capsid
If a virus is not enveloped then it is what?
Naked
What is a viroid?
Infectious agent that is circular, single-stranded RNA molecule about 350 nucleotides in length with substantial internal base pairing
The RNA replicates inside infected cells
What is a prion?
Infectious agents without DNA or RNA
What do prions cause?
Transmissible spongiform encephalopathies (TSEs)
What are TSEs (transmissible spongiform encephalopathies?
A group of related diseases leading to fatal and untreatable neurological deterioration often in the brain
What are some characteristics of prions?
Much smaller than viruses
Very heat resistant
Very radiation resistant
What are some examples of TSEs in farm animals? E.g. caused by prions
Scrapie, which affects sheep and goats
Bovine spongiform encephalopathy (BSE), which affects cattle
What are some examples of TSEs in humans? E.g. diseases caused by prions
Creutzfeld-Jakob diseases
Variant Creutzfeld-Jakob disease
Fatal familial insomnia
What is Creutzfeld-Jakob disease?
Arises in middle age and old age
In most cases is sporadic, occasionally transmitted via treatment with contaminated growth hormone
Some cases inherited as a dominant genetic disorder
What is variant Creutzfeld-Jakob disease?
Affects younger people, transmitted via BSE infected beef, now virtually eradicated
What is fatal familial insomnia?
A dominant genetic disorder that can be transmitted by injection of affected brain tissue into healthy lab animals
What are some diseases caused by viruses?
AIDS Ebola Hepatitis Herpes Influenza Rabies
