Viruses Flashcards
What does viruses contain of?
Nucleic acids enclosed in a protein coat
Sometimes membrane envelope
The RNA can appear in different versions, which ones?
Single/double stranded RNA/DNA
Describe what a capsid is
Protein shell, can be rod-shaped, polyhedral or more complex.
Made up of subunits - Capsomeres
What does “Host range” mean?
each type of virus can only paratisize a limited range of cells, “lock & key”
Antibiotics cannot treat viral infections, why?
Viruses doesn’t have ribosomes, cell walls, peptidoglycan etc
What’s a Megavirus?
Big viruses. can contain all genes for DNA replication/transcription/translation, can contain some metabolic enzymes
What’s a Rickettsia?
Small viruses. Obligate parasites (can’t grow without host), uses host for amino acids, nucleosides etc.
Which are the two types of viral replication?
Lysogenic & lytic cycle
What happens in the lytic cycle?
The phage “takes over” the cells organelles and starts replicating itself within the cell. The cell eventually lyses and the Phage can continue to spread.
What happens in the lysogenic cycle?
The phage genome replicates itself without destroying the host cell. Waits for the cell to replicate and from there on pass on part of its DNA.
What’s an Viroid?
Smaller/simpler than virus.
Consists of molecules of naked RNA that infects plants.
Do not encode for proteins, but can be replicated by the hosts cellular enzymes
Describe the replication of animal viruses
Animal viruses with a viral envelope
Envelope outside the capsid - helps the virus enter host cell
Generally a lipid bilayer with glycoprotein spikes
Envelope fuses with the cell membrane
The ER of the host cell makes the membrane proteins which are transported to the membrane
New viruses exits the host
Describe what a retrovirus is
Most complicated, why? —> genetic info flows in reverse direction (transcribes DNA from an RNA template)
What two reasons are there for influenza-vaccines required to be updated every year?
Antigenic drift - RNA viruses like influenza show more rapid drift than DNA viruses
Random mutations —> new strains of influenza every year
Antigenic shift - Different strains of influenza comes together —> creating a new type.
Major problem —> can cause pandemics since a very different virus is created
What happened in the Hershey -Chase experiment?
Tested if DNA was the genetic material —> as T2 phage is only made up from two macromolecules: Protein & DNA
