viruses Flashcards
(24 cards)
Are viruses considered living?
No, they can’t reproduce or metabolize without a host; they lead a ‘borrowed life’.
What are viruses made of?
Genetic material (DNA or RNA) in a protein coat (capsid), sometimes with a membrane (envelope).
What are the types of viral genomes?
Double/single-stranded DNA or RNA.
What is a capsid?
A protein shell made of capsomeres that protects viral genetic material.
What is a viral envelope?
A membrane from the host cell with viral and host proteins that surrounds some viruses.
What are bacteriophages?
Viruses that infect bacteria (also called phages).
What are the two main phage replication cycles?
The lytic cycle and lysogenic cycle.
What happens in the lytic cycle?
The phage replicates, destroys the host DNA, creates new viruses, and causes the host cell to burst.
What is a virulent phage?
A phage that reproduces only by the lytic cycle.
What happens in the lysogenic cycle?
The phage DNA becomes part of the host DNA as a prophage and is copied each time the host cell divides.
What is a temperate phage?
A phage that can use both lytic and lysogenic cycles.
What triggers a prophage to enter the lytic cycle?
Environmental signals (like stress or damage to DNA).
What is a provirus?
Viral DNA integrated into an animal host’s genome, like in HIV. It stays permanently in the host.
What enzyme do retroviruses use to make DNA from RNA?
Reverse transcriptase.
What kind of virus is HIV?
A retrovirus that causes AIDS.
Why don’t antibiotics work on viruses?
Because viruses don’t have cell walls or metabolism like bacteria.
What are vaccines?
Weakened or dead viruses that train the immune system to fight real infections.
What are emerging viruses?
New viruses that suddenly appear in a population, like Ebola or Zika.
What is a pandemic?
A global outbreak of a disease.
Why do RNA viruses evolve quickly?
They have high mutation rates.
What is a prion?
An infectious, misfolded protein that can cause brain diseases.
How do prions spread?
They convert normal proteins into misfolded prion forms.
What diseases are caused by prions?
Mad cow disease, Creutzfeldt-Jakob disease, and scrapie in sheep.
Are prions indestructible?
They are extremely hard to destroy and act very slowly.
