Topic 12 Viruses Flashcards
(38 cards)
Microorganism
Cells - _, _, _
Not cells - _
- lack the basic cellular structures and functions necessary for independent life
Cells - Bacteria, Fungi, Parasites
Not cells - Virus
_
- _ = Latin _
- infectious and acellular pathogens
- can only replicate within a _ organism
- require living cells to support their replication
- cannot be grown in non-living culture media
- some viruses have affinity for particular cell types
- can infect humans and animals, plants, bacteria
Viruses
- virus = Latin poison
- host organism
Discovery of the First Virus
1886 - _ _ - first described the disease, suspected it was caused by bacteria
1892 - _ _ - showed the infectious agent passed through filters that trapped bacteria
1898 - _ _ - coined term “contagiu vivum fluidum” (_ _ _); concluded it was a new type of pathogen - a virus
AMDIMB
Adolf Mayer
Dmitri Ivanovsky
Martinus Beijerinck - contagious living fluid
Discovery of the First Virus
_ _ _ (TMV) - mottling disease affecting tobacco
- first virus to be identified
Tobacco mosaic virus
Viral infections have been recorded unknowingly from the beginning of recorded history
- pockmarks similar to those of _ have been found on face of a mummified Pharaoh recovered from pyramids of Egypt
- funerary stele of Egyptian priest Ruma (1400 bca) shows a shortened, withered leg, in what is believed to be one of the earliest depictions of _
- scientists discover oldest known human viruses in 50,000 year old Neanderthal remains
- search targeted remnants of 3 types of DNA viruses: _, _, and _
- traces of all 3 viruses were found - oldest human viruses ever discovered
- smallpox - Pharaoh
- polio - Egyptian priest Ruma
- adenovirus, herpesvirus, papillomavirus - Neanderthal
_ (_)
- viruses that selectively target and kill bacteria
- useful as they can destroy bacteria resistant to drugs such as _
- phages infect their bacterial hosts with great specificity; they do not infect human cells
- parts: ch, na, c, w, s, bp, s, tf
- TEM of T4 bacteriophage infecting EC
Bacteriophages (phages)
- antibiotics
- parts: capsid head, nucleic acid, collar, whiskers, sheath, base plate, spikes, tail fiber
Definition of terms
_ - infectious agents with genetic material enclosed in protein coat (sometimes with an envelope)
_ - complete functional virus that has the capacity to infect living tissues
- virus in its extracellular phase
_ - infectious agents consisting only of RNA
- infects only plant cells
_ - misfolded proteins
- consist only of protein, no DNA/RNA
Virus
Virion
Viroid
Prions
_ - infectious proteins
- cause neurodegenerative disease in humans and animals
- _ _ _ or bovine spongiform encephalopathy (BSE)
- affects cattle and can be transmitted to humans through contaminated beef
- human form called variant - _ (vCJD)
Prions
- Mad cow disease
- Creutzfeldt-Jakob disease
How are viruses different from other microorgansms?
Growth on artificial media | Division by binary fission | Posses both DNA and RNA | Sensitive to antibiotics
Bacteria
Mycoplasma
Rickettsia
Chalmydia
Viruses
Growth on artificial media | Division by binary fission | Posses both DNA and RNA | Sensitive to antibiotics
Bacteria - Yes, Yes, Yes, Yes
Mycoplasma - Yes, Yes, Yes, Yes
Rickettsia - No, Yes, Yes, Yes
Chalmydia - No, Yes, Yes, Yes
Viruses - No, No, No, No
How big are viruses?
Size range - most _ micrometer
- requires _ _
Virus sizes vs Protein molecule
MPHRH IATPY H
- <0.2 micrometer
- requires electron microscope
Viruses - Megavirus (800 nm), Poxvirus, Herpes simplex, Rabies, HIV, Influenza, Adenovirus, T2 bacteriophage, Poliomyelitis, Yellow fever
Protein molecule - Hemoglobin molecule
Structure of viruses
- a _ _ _ (DNA or RNA)
- a protective shell or _
- _ - extra lipid bilayer membrane surrounding the protein capsid (some but not all viruses)
- parts: ep, e, vt, n, vg
- nucleic acid genome (DNA or RNA)
- capsid
- envelope
- parts: envelope protein, envelope, viral tegument, nucleocapsid, viral genome
_ _
- contains viral genome that encodes proteins not present in the host cell
- _ or _ -> _ or _ -> _ stranded or _ stranded
- Linear DNA SS - parvovirus; ds - herpesvirus
- Circular DNA SS - M13; ds - baculovirus
- Linear RNA SS - TMV; ds - reovirus
- Circular RNA SS - hepatitis D virus; NA
- DNA or RNA -> linear or circular -> single stranded or double stranded
_
- _ = Latin _
- encases and protecs virus’ nucleic acid
- made up of protein subunits called _
- _ + _ _ = _
Capsid
- capsa = Latin box
- subunits called capsomeres
- capsid + viral genome = nucleocapsid
_
- not all viruses have this
- typically derived from the host cell membrane during the process of viral budding and often contains viral glycoproteins (_ proteins)
- _ proteins
- exposed proteins on the outside of the envelope
- essential for attachment and entry of the virus into new host cell
Envelope
- Spike proteins
Roles of Capsid and Envelope (Structural Proteins)
- _ of genome
- assembly of a stable protective protein layer
- packaging of newly formed viral particles
- _ of genome
- virus attachment to cells; entry into cells
- uncoating of genome/release of capsid contents into the cells
- transfer of viral genetic material
- Protection of genome
- Delivery of genome
Viral Categorization
A. _ _ - helical, icosahedral, complex
B. _ _ _ - naked, enveloped
C. _ _ _ _
_ _ - allows for more precise and detailed characterization of viruses based on their genome sequences
- this approach complements traditional methods which rely on physical characteristics and host range
A. Capsid symmetry
B. Presence of envelope
C. Types of viral genome
Viral sequencing
A. Types of Capsid
_ - protein subunits and the nucleic acid are arranged in a helix
_ - protein subunits assemble into a symmetrics shell that covers the nucleic acid-containing core
_ - c architecture that does not strictly conform to a simple h or i shape
Helical
Icosahedral
Complex
A. Types of Capsid
- _ _ defines the basic viral shape
- _ - RNA, capsomers forming capsid; TEM of Ebolavirus (mop head)
- _ - glycoprotein spikes, envelope, capsomers forming capsid; adenovirus, bead-like capsomeric structures form flay triangular facets on surface (D20)
- _ - head (capsid) contains DNA genome, collar, tail, DNA injected into host cell, 100 nm; capsid connected to contractile tail with protruding tail fibers (spider)
- Capsid symmetry
- Helical
- Icosahedral
- Complex
B. Presence of _
- _ _ _ - sensitive to temp, pH, desiccation, lipid solvents and detergents
- capsids are more resistant and stable; can survive longer in environment
- _ viruses tend to be more sensitive to extreme pH, heat, dryness, and simple disinfectants
- _ _ Virus - capsid and nucleic acid
- _ Virus - spike, envelope with membrane, matrix, capsid, nucleic acid
B. Presence of Envelope
- Stability of Virus
- enveloped viruses tend to be more sensitive
- Naked Nucelocapsid Virus
- Enveloped Virus
C. _ _
- carries gene necessary to invade host cell and redirect cell’s activity to make new viruses
- very _
- _ or _ (never both)
- _- or _- stranded
- _ or _
- vary in _
- vary in _ of _ or _ molecules
DSLLN
C. Viral genome
- very diverse
- DNA or RNA (never both)
- Single- or double- stranded
- Linear or circular
- vary in length
- vary in number of DNA or RNA molecules
- a way to categorize viruses based on their genome type and replication strategy
- created by David Baltimore in 1971
- _ kind of viral genome
- _ _ - all viruses must make mRNA that can be translated by host ribosome; they are all parasites of the host protein synthesis machinery
Baltimore Classification System
- 7 kind of viral genome
- Messenger RNA
Baltimore Classification System
I - _ _ _ - mRNA is transcribed directly from DNA template
II - _ _ _ - DNA converted to ds form before RNA is transcribed
III - _ _ _ - mRNA is transcribed from the RNA genome
IV - _ _ _ (+) - genome functions as mRNA
V - _ _ _ (-) - mRNA is transcribed from the RNA genome
VI - _ _ _ _ _ _ _ - reverse transcriptase makes DNA from RNA genome; DNA incorporated in host genome; mRNA transcribed from incorporated DNA
VII - _ _ _ _ _ _ _ - viral genome is dsDNA, but viral DNA is replicated through RNA intermediate; RNA may serve directly as mRNA or as template to make mRNA
DSDSSSD
I - dsDNA
II - ssDNA
III - dsRNA
IV - ssRNA (+)
V - ssRNA (-)
VI - ssRNA viruses with reverse transcriptase
VII - dsDNA viruses with reverse transcriptase
Viral Genomes
_ - have a _ genome size
- include groups _ _ _ of Baltimore classification
- _ replication
- _ repair mechanism
- _ mutability
_ - have comparatively _ genome size
- comprise groups _ _ _ _ of Baltimore classification
- _ replication
- _ RNA repair mechanism
- _ mutability
DNA - larger genome size
- I, II, VII
- slow replication, DNA repair mechanism, low mutability
RNA - smaller genome size
- III, IV, V, and VI
- rapid replication, no RNA repair mechanism, high mutability
- _ - approximately one error in 10^7 nucleotides
- _ - approximately one error in each 10^3 to 10^4 nucleotides
Transcription error rate
- DNA
- RNA
