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37 Cards in this Set
- Front
- Back
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Virus |
genetic element that cannot replicate independently of a living (host) cell |
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Virology |
the study of viruses |
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Virus particule (virion) |
extracellular form of a virus -exists outside the host and facilitates transmission from one host cell to another -contains nucleic acid genome surrounded by a protein coat, in some cases, other layers of material |
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Capsid |
the protein shell that surrounds the genome of a virus particle -composed of a number of protein molecules arranged in a process and highly repetitive pattern around the nucleic acid |
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Capsomere |
subunit of the capsid -smallest morphological unit visible with an electron microscope |
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Nucleocapsid |
complete complex of nucleic acid and protein packaged in the virion |
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Enveloped Virus |
-virus that contains additional layers around the nucleocapsid -envelope makes initial contact with the host cell |
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Complex Viruses |
-virions composed of several parts, each with separate shapes and symmetries -bacterial viruses contain complicated structured
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Lysozyme |
-Makes hole in cell wall -lyses bacterial cell |
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Neuraminidases |
-enzymes that cleave glycosidic bonds -allows liberation of viruses from cell |
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Titer |
Number of infectious uniter per volume of fluid |
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Plaque Assay |
analogous to the bacterial colony on e way to measure virus infectivity |
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Plaques |
clear zones that develop on lawns of host cells -lawn can be bacterial or tissue culture -each plaque results from infection by a single virus particle |
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Phases of Viral Replication |
-Attachment (adsorption): of the virus to a susceptible host cell -Entry (penetration): of the vision or its nucleic acid -Synthesis: of virus nucleic acid and protein by cell metabolism as redirected by virus -Assembly: of caplids and packaging of viral genomes into new virions (maturation) -Release: of mature virions from host cell |
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Permissive Cell |
host cell that allows the complete replication cycle of a virus to occur |
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Bacteriophage T4 |
virus of E. coli, one of the most complex penetration mechanisms |
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Restriction Modification System |
DNA destruction system, only effective against double-stranded DNA viruses |
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Restriction Enzymes |
cleave DNA at specific sequences |
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Early Proteins |
-synthesize soon after infection -necessary for replication of virus nucleic acid -typically act catalytically |
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Late Proteins |
-synthesized later -included proteins of virus coat -typically structural components -synthesized in larger amounts -head and tail proteins and enzymes required to liberate mature phage particles |
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Virulent Mode |
viruses lyse host cels after infection |
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Temperate Mode |
viruses replicate their genomes in tandem with host genome and without killing host -virus can also be lytic |
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Temperate viruses |
can undergo a stable genetic relationship within the host -can kill cell through lytic cycle |
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Lysogeny |
state where most virus genes are not expressed and virus genome is replicated in synchrony with host chromosome |
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Lysogen |
a bacterium containing a prophage -under certain conditions lysogenic viruses may revert to the lytic pathway and begin to produce virions |
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Bacteriophage Iambda |
-linear dsDNA genome -complementary, ss regions 12 nucleotides long at the 5' terminus of each strand -upon penetration, DNA ends base-pair, forming the cos site, and the DNA ligates and forms double-stranded circle -when Lambda |
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Elements of Repressor Proteins |
-cl protein-causes the repression of lambda lytic events -cro repressor- controls activation of lytic events |
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Persistent infecions |
release of virions from host cell, does not result in cell lysis |
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Latent Infections |
delay between infections by the virus and lytic events |
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Transformation |
Conversion of normal cell into tumor cell |
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Cell fustion |
two or more cells become one cell with many nuclei |
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Retrovirus |
RNA viruses that replicate through a DNA intermediate |
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Defective Viruses |
viruses that are parasitic on other viruses |
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Prions |
infectious proteins whose extracellular form contains no nucleic acid |
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Infectious Prion Disease |
pathogenic form of prion protein is transmitted between animals or humans |
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Sporadic prion disease |
random misfiling of a normal protein in a uninfected individual |
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Inherited prion disease |
mutation in prion gene yields a protein that changes more often into disease-causing form |
