Viruses, Viroids and Prions Flashcards
What is a virus?
One or more nucleic acid molecules within a coat made of protein.
Are viruses alive?
Up for debate. They do not reach all the required features to be classed as living. Most consider them non-living.
Do viruses contain DNA?
They can possess DNA or RNA but not both.
What class of parasites are viruses?
They can be considered obligate parasites; they cannot reproduce outside a living cell.
What is the scientific name for the ‘protein coat’? What is its general structure?
The capsid is made up of capsomeres which usually combine to form an icosahedral (20 sided) capsid. Glycoprotein spikes may stick out of the capsid.
What forms of nucleic acid can be found in viruses?
Double stranded DNA.
Single stranded DNA.
Double stranded RNA.
Single stranded RNA.
What does enveloped mean in relation to virus structure?
Surrounded by a lipid/nuclear membrane from a cell.
What is the term given to a naked virus?
An adenovirus.
What are the 4 stages of the virus life cycle?
1) Entry and uncoating.
2) Replication.
3) Transcription and Manufacture of Capsid Proteins
4) Self-assembly of New Virus Particles and Exiting from the Cell
What are the two types of single stranded RNA viruses? How do they differ?
(+)ssRNA viruses: GENOME CAN ACT DIRECTLY AS mRNA.
(-)ssRNA viruses: GENOME IS COMPLEMENTARY TO mRNA.
How to retroviruses replicate? What is an example of a retrovirus?
They replicate via a DNA intermediate.
HIV is the most infamous retrovirus.
RIP Freddie Mercury.
How do (+)ssRNA viruses replicate?
1) Enters cell
2) Viral RNA (+) strand translated
3) RNA-dependent polymerase produced
4) Makes complementary RNA to viral (-) strand
How does HIV replicate?
HIV contains reverse transcriptase. Allows the virus to make a DNA copy of its genome which is integrated into a host chromosome.
What is a viroid?
A pure nucleic acid that is infectious.
Can humans be infected by viroids?
Currently all known viroids infect exclusively plants.
