Viruses, Viroids and Prions Flashcards
Viruses
- Aren’t considered living
- Have DNA or RNA but not both
- protein coat
- has no ribosomes
Why are viruses considered non-living
- They need a host to cause infection
- Once it finds a host it will begin to multiply and cause infection
Obligatory intracellular parasite
Requires a host to multiply
Host range
The spectrum of the virus to cause infection to a host cell
Bacteriophage
Viruses that infect bacteria
How does viruses infect the host
- Virus chemically interacts with specific receptors sites on the surface of the cell
- The virus and the cell are held together by weak hydrogen bonds that later get stronger
Phage therapy
- Using bacteriophages to treat bacterial infections
- using viruses to treat diseases
Virons
- Complete, fully developed viral infectious particles
- Composed of nucleic acids and surrounded by protein coats
Nucleic acid structures of viruses
- encoded by RNA or DNA but not both
- Single stranded or double stranded
- can be linear or circular
Capsid
- Protein coat made of capsomeres
- Visible in electron mircographs
- protect nucleic acids from nucleases enzymes
Envelope
-Some combination of lipid, protein, or carbohydrates caoting on some viruses
Spikes
- projections from outer surfaces
-Protein complexes - Can be clumps of red blood cells (hemagglutination)
Viral morphology
-Helical
- Polyhedral
- Enveloped
- Complex
- Viroid
Helical virus
- Hollow, cylindrical capsid
- rabies and ebola
Polyhederal virus
- many sided
- animals, plants, and bacterial viruses
- poliovirus, adenvirus
Complex virus
- complicated structures
- may have a polyhedral head and a helical tail or vice versa
- Poxvirus
Viroid
- Composed mostly of short strands of circular, single- strand RNA with no protein coating
- smallest infectious pathogens known
Enveloped virus
- roughly spherical
- influenza, human herpes
What viral morphology causes rabies and ebola
Helical
What viral morphology has a polyhedral head and a helical tail or vice vera
Complex virus
What viral morphology causes poxvirus
complex virus
What viral morphology is know to be the smallest infectious pathogen
viroid
What viral morphology causes human herpes and influenza
enveloped virus
What viral morphology causes poliovirus and adenovirus
polyhedral virus
Taxonomy of viruses
- classified into families by their genomics and structures
- genus name: -virus
- family name: -viridae
- order name: - ales
- virus
genus name
- herpesvirus
-viridae
family name
- simplexvirus
- ales
order name
- human herpesvirusale
What do you grow bacteriophages in at the lab
liquid broth
solid medium
What can you grow animal viruses in at the lab
- living animals
- embryonated eggs
- cell cultures
growing viruses in living animals
- most studies about the immune system
- some viruses cant be grown outside of the human body
- use mice, rabbits and guinea pigs
growing viruses in embryonated eggs
- viruses are injected into a small hole in an egg
- helps develop viruses
- viral growth is determined w/ the death of the egg
growing viruses in cell culture
-cell growth in cultured media
- more convenient than whole animals and eggs
- suspended in a solution that provides nutrients, growth factors and osmotic pressures
Cytopathic effect
visible effects on the host cell caused by the virus resulting in cell damage or death
Primary cell lines
- tissues slices
- tend to die after a few generations
Diploid cell lines
- human embryos
- maintain life for about 100 generation
- used for culturing viruses that require a human host
Continuous cell lines
- routinely grown in a lab
- cancer cells
- indefinite number of generations
Viral identification
- blotting
- electron microscope
- ploymerase chain reaction
For viruses to multiply they
- invade a host cells
- must take over the host metabolic machinery
Lytic cycle
- phage causes lysis and death of the host cell
Lysogenic cycle
- Phage DNA is incorporated in the host
- phage conversion
- specialized transduction
Lytic cycle stages
- attachment
- penetration
- biosynthesis
- maturation
- release
What is the attachment stage of the lytic cycle
- phage attaches by the tail fibers to the host cell
What is the penetration stage of the lytic cycle
- phage lysozymes open the cell wall
- the tail sheath forces the tails core and DNA into the cell
What is the biosynthesis stage of the lytic cycle
- production of phage DNA and proteins
What is the maturation stage of the lytic cycle
- assembly of phage particles
What is the release stage of the lytic cycle
- phage lysozymes break the cell wall
What stage does the sheath tail forces DNA and core tail into a cell
Penetration
In what stage does lysozyme attach to the tail fibers of host cells
Attachment
In what stage of the lytic cycle are DNA and protein produced
Biosynthesis
At what stage in the lytic cycle are phages particles assembled
Maturation
At what stage in the lytic cycle do phage lysozyme break the cell wall
Release
Lysogeny
Phage remains latent
Prophage
- Inserted phage DNA
- Also replicated when host cells replicate their chromosomes
Phage conversion
the host cell exhibits new properties
stages of multiplication of animals viruses
- attachment
- entry
- uncoating
- biosynthesis
-maturation - release
What happens in the attachment stage of multiplication of animal viruses
virus attaches to the cell membrane
What happens in the entry stage of multiplication of animal viruses
enter by receptor-mediated endocytosis or fusion
What happens in the uncoating stage of multiplication of animal viruses
- uncoating of viral or host enzymes
What happens in the biosynthesis stage of multiplication of animal viruses
- production of nucleic acid and proteins
What happens in the maturation stage of multiplication of animal viruses
nucleic acid and capsid proteins assemble
What happens in the release stage of multiplication of animal viruses
viruses are released by budding(enveloped viruses) or rupture
In what stage of the multiplication of animal viruses does the virus go through fusion or receptor-mediated endocytosis
Entry
In what stage of the multiplication of animal viruses does production of nucleic acids and proteins get produced
biosynthesis
In what stage of the multiplication of animal viruses does nucleic acids and capsid proteins assemble
maturation
In what stage of the multiplication of animal viruses are budding and ruptures apart of
release
Where do viruses replicate their DNA
in the nucleus of thee host cell using viral enzymes
Adenoviridae
- double stranded DNA
- non-enveloped
- Causes respiratory infections in humans
- causes tumors in animals
Poxviridae
- double stranded DNA
- enveloped
- causes skin lesions
- vaccinnia and smallpox viruses
Herpesviridae
- Double stranded DNA
- enveloped
- HHV-1 & 2 : Simplexvirus: cold sores
- HHV- 3: Varicellovirus: chickenpox
- HHV-4: Lymphocrytovirus: causes mononucleosis
- HHV-5: Cytomegalovirus
- HHV-6 & 7: Roseolovirus
- HHV-8 Rhadinovirus: causes Kaposi’s sarcoma
Papovaviridae
- double stranded DNA
- non-enveloped
- papillomavirus
- causes warts and can transform cells and cause cancer
- papillomavirus
Hepadnaviridae
- double stranded
- enveloped
- hepatitis B virus
- uses reverse transcriptase to make DNA from RNA
- hepatitis B virus
What is a sarcoma
cancer of connective tissue
What is adenocarcinomas
cancer of glandular epithelial tissue
What are oncogenes
transform normal cell into cancerous cells
What is the oncogenic viruses
- viruses that become intergrated into the host cell DNA
- induces tumors
what are reasons cancer goes unnoticed
- contagious viral diseases
- cancers may not develop until long after viral infection
- viruses infect cells but not induce cells
Normal cells to tumor cells
- alterations of genetic material
- oncogenes
Oncogenes
- can bring about malignant transformation
- can be activated by abnormal functions
- mutagenic chemical
- high-energy radiation
- viruses
Oncogenic viruses
- oncoviruses
- viruses capable of inducing tumors in animals
transformation of tumor cells
- change normal cells into cancerous cells
- tend to be irregularly shaped
Tumor specific transplantation antigens (TSTA)
- Viral antigens on the surface of a transformed cell
DNA oncogenic viruses
- found in several families of of DNA containing viruses
- adenoviridae, herpesviridae, poxviridae and more
- HPV and HBV
RNA oncogenic viruses
- only found in the Retroviridae family
- Human T-cell leukemia viruses
- Feline leukemia virus
- produce cancer using reverse transcriptase