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Describe viruses
Obligate intracellular parasites
Infect specific cell receptors
30 nm (smaller than bacteria)
Characteristics of viruses
Outside capsid layer & some have a lipid envelope
Inside are genomes & proteins (either DNA or RNA, never both)
What are viruses sensitive to?
Interferons
What are the 4 morphological types of viruses?
Helical
Polyhedral
Complex
Enveloped
Helical viruses
Cylindrical
Rabies
Ebola
Polyhedral viruses
Equilateral triangle
Adenovirus
Poliovirus
Complex viruses
Bacteriophage, alien-rocketship thing
Enveloped viruses
May be covered in spikes
Glycoproteins for attachment
COVID
Influenza
Herpes
Naked viruses
No lipid coat outside capsid
Rhinovirus
Poliovirus
Norwalk
Viruses grow in
Living cells
How are viruses seen on a plate?
Bacteriophages form plaques on a lawn of uninfected bacteria
Virus multiplication
Invade a host cell
Take over the hosts’ metabolic machinery
One-step growth curve
Difference between lytic & lysogenic cycle
Lytic cycle will destroy the hosts’ DNA & replace it with their own
Lysogenic cycle integrates their DNA into the hosts’ cell’s
Order of multiplication of bacterial virus
Attachment
Penetration
Replication, transcription, translation
Biosynthesis
Maturation
Lysis
Phage conversion in lysogeny cycle
Host acquires new properties from the introduction of the viral DNA
Order of multiplication of animal viruses
Attachment
Penetration
Uncoating
Biosynthesis
Maturation
Release
Attachment in animal viruses
Spikes recognize receptors
Penetration in animal viruses
Endocytosis or fusion
Uncoating in animal viruses
Release genetic material
Biosynthesis in animal viruses
DNA/RNA biosynthesis & multiplication
Maturation in animal viruses
Assembly of new viral particles
Release in animal viruses
Budding or rapture
Result of budding in release of an animal virus
Original host cell remains alive & new cell obtains an envelope
Result of rapture in release of an animal virus
Original host cell dies & new cell has no envelope (naked)
Difference between bacteriophages & animal viruses
Bacteriophages
Attach with tail fibers
Viral DNA is injected
Activities occur in cytoplasm
Animal Viruses
Attach with glycoproteins
Capsid enters via endocytosis or fusion
Activities either in nucleus (DNA) or cytoplasm (RNA)
Genome multiplication
Replication (double stranded DNA)
Transcription (RNA: +/sense strand —- DNA: -/anti-sense strand)
Translation (+/sense strand is read)
DNA polymerase
Used in replication
RNA polymerase
Used in transcription
Does mRNA use the template -/+ strand?
Non-template strand (+/sense strand)
Polymerases in viral replication
DNA
Use host cell polymerase
Code for their own DNA polymerase & transcriptase
RNA
Use host cell polymerase
Code for their own DNA polymerase
Carry their own polymerases
Reverse transcriptase
Using RNA to make DNA
HIV
Leukemia viruses
dsDNA
Double stranded DNA
Herpes
HPV
Smallpox
Adenovirus
Hepatitis B-virus
ssDNA
Single stranded DNA
Parvovirus
ssRNA -
Single stranded RNA w/ the -/anti-sense strand
Measles
Influenza
Ebola
ssRNA +
Single stranded RNA w/ the +/sense strand
SARS coronavirus
Rhinovirus
Hepatovirus
Poliovirus
Rubella
dsRNA
Double stranded RNA
Rotavirus
Retroviruses
ssRNA; converts RNA to DNA using reverse transcrptase
HIV-1 (AIDS virus)
dsDNA replication
Largest group of known viruses
Replicates in host nucleus
ssDNA replication
Replicates in host nucleus
ssRNA+ replication
RNA polymerase takes ssRNA+ & converts it to ssRNA-
Then it converts it back to ssRNA+
ssRNA+ makes new capsid proteins
Assembled in cytoplasm
ssRNA- replication
RnA-dependent RNA polymerase converts ssRNA to ssRNA+
ssRNA+ makes more ssRNA- & continues
In cytoplasm
dsRNA replication
Separated to ssRNA+ & ssRNA -
In cytoplasm
Retrovirus replication
Uses reverse transcriptase to use ssRNA to make dsDNA
dsDNA goes to nucleus & integrates into host genome
Oncogenic viruses
Cancer
What do oncogenes do?
Make cells replicate uncontrollably
Loses contact inhibition
Glycoproteins can’t signal to stop multiplying
How do you see if you have cancer with the virus?
Presence of:
Tumor Specific Transplantation Antigens (TSTA)
T antigens in nucleus
Oncogenic DNA viruses
Human Herpesvirus
Papillomavirus
Hepatis B virus
Oncogenic RNA viruses
Retrovirus
Acute viral infection
Virus in bloodstream
Sudden onset
Influenza
Latent viral infection
Virus remains in asymptomatic host cell for long periods
HIV
AIDS
Leukemia
Recurrent viral infection
Infection reoccurs
Shingles
Persistent viral infection
Occurs over a long period of time
Cancer
AIDS