Week 10: Bacteriophages And Viruses Flashcards
What is a virus?
Genetic elements that can multiply their genome independently of a cell’s chromosome but require a host.
What is a ‘naked’ virus?
A virus that consists of a nucleocapsid, which is composed of a capsid and nucleic acid.
What are adenoviruses responsible for?
A large number of upper respiratory infections.
What shape does the capsid of adenovirus form?
An icosahedron.
What is a characteristic of enveloped viruses?
They have a lipid bilayer that comes from the host cell.
What are examples of enveloped viruses?
- Influenza virus
- Herpes virus
What are complex viruses?
Viruses like bacteriophage T4 that have a more intricate structure.
What types of genomes can viral genomes consist of?
- DNA
- RNA
What are the categories of RNA viruses?
- ssRNA
- dsRNA
What is the lytic pathway of infection?
All resources of the host cell are used to produce phage particles, leading to the cell being lysed.
What type of life cycle can bacteriophage λ enter?
Lysogenic or lytic life cycle.
What influences the decision between the lysogenic and lytic cycle?
A transcriptional regulatory network.
What happens during early gene expression in virus infection?
Discrimination between ‘early’ and ‘late’ genes that are expressed.
What is the role of cI protein in bacteriophage λ?
It represses transcription of the genes for lysis and establishes expression of the lysogenic genes.
What occurs if a second phage injects its chromosome into an already infected cell?
cI binds to PRM, preventing production of the replication proteins of the second phage genome.
What is the result of cII protein being at a low level?
Transcription of Cro is not repressed, leading to the establishment of the lytic cycle.
What can cause reactivation of latent herpes simplex virus (HSV)?
- Stress
- UV light
- Trauma
- Fever
What can happen following the integration of retroviral genomes into the host genome?
It can cause tumor formation and other cancers.
What are the steps for double-stranded DNA viruses during replication?
- Transcription of dsDNA into mRNA
- Transport into nucleus
- Translation
What is the difference between prokaryotic and eukaryotic cell infection processes?
Prokaryotic cells have no compartmentation, whereas eukaryotic cells do, requiring transport into the nucleus.
What is a common complication of herpes simplex virus (HSV) infection?
HSV encephalitis, which can lead to severe brain damage or death.
Fill in the blank: The viral genome of HIV-1 integrates into the host genome, which can remain dormant for _______ with very low virus titres.
years.
What is HSV encephalitis?
A rare but dramatic condition caused by herpes simplex virus that can lead to fever, seizures, paralysis, coma, and severe brain damage or death.
What virus causes chickenpox?
Varicella-Zoster Virus (VZV)
How does chickenpox relate to HSV?
Chickenpox is caused by a virus closely related to HSV and both viruses remain in the nervous system.
What percentage of chickenpox cases may recur as zoster or shingles?
About 10%
What is a common problem with virus replication?
Replication of viruses is surprisingly inaccurate.
Which type of viruses show very high error rates in replication?
RNA viruses
What are two challenges viruses face when growing in a host?
Viruses have to replicate very quickly and escape the immune system of the host.
What effect does high error rates during replication have on viruses?
It ensures variation of the outer surface proteins.
True or False: HSV encephalitis occurs more often as a primary infection than as a re-activation.
False
Fill in the blank: Chickenpox is caused by the _______.
Varicella-Zoster Virus (VZV)
