A2.3 Viruses Flashcards
(14 cards)
What are the structural features common to all viruses?
Small, fixed size; nucleic acid (DNA or RNA); protein capsid; no cytoplasm; few or no enzymes.
What types of genetic material can viruses have?
DNA or RNA; either single-stranded or double-stranded.
How do enveloped viruses differ from non-enveloped viruses?
Enveloped viruses have a membrane from the host cell; non-enveloped viruses do not.
Name three example viruses and one key trait for each.
Bacteriophage lambda – infects bacteria; Coronavirus – enveloped RNA virus; HIV – enveloped retrovirus.
What is the lytic cycle in viruses?
A cycle where the virus infects a host, replicates rapidly, assembles new virions, and causes host cell lysis.
Which virus is commonly used to study the lytic cycle?
Bacteriophage lambda.
What is the lysogenic cycle in viruses?
A cycle where viral DNA integrates into the host genome and remains dormant, replicating with the host until activation.
What triggers the switch from lysogenic to lytic cycle?
Environmental stressors such as UV radiation or chemical exposure.
What does the diversity of viruses suggest about their origin?
Viruses may have multiple evolutionary origins, not a single ancestor.
What is convergent evolution in viruses?
Shared features (e.g. parasitism, capsids) evolved independently due to similar selective pressures.
What genetic feature do viruses share with living organisms?
The universal genetic code.
Why do viruses evolve rapidly?
High mutation rates, short generation times, and large population sizes.
Give two examples of rapidly evolving viruses.
Influenza viruses and HIV.
What are the consequences of rapid viral evolution for medicine?
Vaccines and treatments may become less effective; frequent updates are needed.
