Micr33 – Microbiology Test Questions – Flashcards
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| Obligatory intracellular parasites |
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| Viruses can only reproduce inside cells. Outside, they are metabolically inert virions. Hijacks cell's TXN and TLN mechanisms to express early, middle, and late genes |
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| Contain DNA or RNA (not both!) |
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| It can be ss or ds, circular or linear, and some genomes are multisegmented |
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| Viruses have no |
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| Ribosomes or any ATP-generating mechanism |
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| Viruses contain a protein coat called a |
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| Capsid |
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| Characteristics of viruses |
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| Some enclosed by envelope, some may have spikes. Most viruses infect only specific types of cells in one host (called tissue tropism) |
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| Host range is determined by |
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| SPECIFIC host attachment sites and cellular factors. Some viruses carry specialized enzymes within their capsids |
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| Virion structure |
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| Nucleic acid (DNA or RNA genetic material) |
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| Taxonomy of viruses: family names end in |
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| -viridae |
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| Taxonomy of viruses: genus names end in |
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| -virus |
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| Taxonomy of viruses: Viral species |
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| A group of viruses sharing the same genetic information and ecological niche (host). Common name =species, subspecies= number |
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| Viruses must be grown in |
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| Living cells. Bacteriophages form plaques on lawn of bacteria |
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| Animal cells |
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| May be grown in living animals or in embryonated eggs, or in cell cultures. Continuous cell lines |
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| Polyhedral virus |
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| Most common shape. Icosahedron= 20 triangular sides at 12 points |
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| Capsomeres |
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| Small subunits that make up capsid |
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| Orthopoxvirus |
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| Has layers of protein or "several protein coats" |
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| Cytopathic effects |
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| Pathologic, degenerative changes in cells |
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| Serological tests |
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| Detect antibodies against viruses in a patient. Use antibodies to ID viruses in neutralization tests, viral hemagglutination, and Western blot |
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| The lytic cycle: Attachment |
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| Phage attaches by tail fibers to host cell |
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| The lytic cycle: Penetration |
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| Phage lysozyme opens cell wall |
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| The lytic cycle: Biosynthesis |
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| Production of phage DNA and proteins |
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| The lytic cycle: Maturation |
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| Assembly of phage particles |
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| The lytic cycle: Release |
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| Phage lysozyme breaks cell wall (kills it) |
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| Lytic cycle |
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| Phage causes lysis and death of host cell |
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| Lysogenic cycle |
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| Prophage DNA incorporated in host DNA. Phage conversion. Specialized transduction |
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| Multiplication of Animal viruses |
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| Attachment, penetration, uncoating, biosynthesis, maturation, release |
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| Attachment |
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| Viruses attach to cell membrane |
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| Penetration |
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| By endocytosis or fusion |
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| Uncoating |
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| By viral or host enzymes- removal of coat |
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| Biosynthesis |
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| Production of Nucleic acid and proteins |
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| Maturation |
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| Nucleic acid and capsid proteins assemble |
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| Release |
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| By budding (enveloped viruses) or rupture |
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| Activated oncogenes |
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| Transform normal cells into cancerous cells |
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| Cancer: Transformed cells |
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| Have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens. Genetic material of oncogenic viruses becomes integrated into the host cell's DNA |
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| Viruses and Cancer |
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| Viruses may contribute to 15% of all human cancers Viruses alter growth properties of human cells by triggering expression of oncogenes or disrupting tumor-suppressing genes |
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| Oncogenic DNA viruses |
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| Adenoviridae, herpesvirudae, poxviridae, papoviridae, hepadnaviridae |
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| Oncogenic RNA viruses |
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| Retroviridae, viral RNA is transcribed to DNA which can integrate into host DNA. HTLV-1, HTLV-2 |
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| Latent and persistent viral infections |
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| -Virus remains in asymptomatic host cell for long periods. Ex) cold sores |
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| Prions |
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| Proteinaceous infectious particle. Inherited and transmissible by ingestion, transplant, and surgical instruments |
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| Prions |
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| PrPc: normal cellular prion protein, on cell surface PrPsc: scrapie protein |
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| Plant viruses |
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| Enter through wounds or via insects |
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| Viroids |
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| Infectious RNA. Ex) potato spindle tuber disease. |
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| Viroids structure |
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| Tiny naked molecules of circular RNA. Resemble introns of rRNA genes. 200-400 nucleotides long. Resistant to degradation. Cause disease in plants. |
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| Parvoviridae |
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| Single-stranded DNA, nonenveloped viruses. 5th disease. Anemia in immunocompromised patients |
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| Adenoviridae |
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| Double-stranded DNA, nonenveloped viruses. Respiratory infectious in humans, tumors in animals |
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| Papoviridae: Polyomavirus |
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| (polyomaviridae) cause rumors, some cause cancer |
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| Poxviridae |
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| Double stranded DNA. Enveloped Orthopoxvirus (vaccinia and smallpox viruses) molluscipoxvirus. Cause small pox, molluscum contagiosum, cowpox |
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| Herpesviridae |
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| Double-stranded DNA, enveloped viruses. (HHV-1-8). Some herpes viruses can remain latent in host cells. Cause a variety of diseases: Fever blisters, chickenpox, shingles, infectious mononucleosis |
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| Hepadnaviridae |
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| Double stranded DNA, enveloped Hep B is example Use reverse transcriptase- replicate through RNA intermediate |
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| Picornaviridae |
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| Single stranded RNA, strand, nonenveloped. Enterovirus:poliovirus and coxsackievirus Rhinovirus: causes common cold Hep A |
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| Caliciviridae |
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| Single stranded RNA, strand, nonenveloped Hep E Norovirus causes gastroenteritis |
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| Togaviridae |
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| Single-stranded RNA, strand, enveloped Alphavirus- transmitted by Arthropods, includes EEE and WEE Rubivirus (rubella virus) |
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| Flaviviridae |
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| Single stranded RNA, strand, enveloped. Arboviruses can replicate in Arthropods. Can cause yellow fever, dengue, st Louis and west Nile encephalitis Hep C |
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| Coronaviridae |
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| Single stranded RNA, strand, enveloped -Upper respiratory infections -Coronavirus -SARS |
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| Rhabdoviridae |
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| Single-stranded RNA. - strand -vesiculovirus -Lyssavirus (rabies) -cause numerous animal diseases |
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| Filoviridae |
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| Single stranded RNA, - strand Filovirus Enveloped helical virus Ebola and Marburg viruses Cause hemorrhagic fevers |
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| Paramyxoviridae |
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| Single stranded RNA, - strand Paramyxovirus Morbilivirus Parainfluenza Mumps Newcastle disease |
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| Deltaviridae |
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| Single-stranded RNA, - strand, one RNA strand Hep D Depends on confection with hepadnavirus |
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| Orthomyxoviridae |
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| Single stranded RNA, - strand, multiple RNA strands Envelope spikes can agglutinate RBCs Influenza A and B and C |
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| Bunyaviridae |
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| Single stranded RNA, - strand, multiple RNA strands Bunyavirus Hantavirus-causes pulmonary syndrome first identified in 1993 in the American Southwest |
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| Arenaviridae |
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| Single stranded RNA, - strand, multiple RNA strands Helical capsids contain RNA-containing granules, lymphocytic choriomeningitis, VEE, lassa fever |
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| Retroviridae |
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| Single stranded RNA, 2 RNA strands, produce DNA Use reverse transcriptase to produce DNA from viral genome. HIV Oncogenic viruses-includes all RNA tumor viruses |
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| Reoviridae |
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| Double-stranded RNA, nonenveloped Reovirus(respiratory enteric orphan) Rotavirus(mild respiratory infections and gastroenteritis) Colorado tick fever |
