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Chap 8 - Viruses

Viruses and Their Replication

the extracellular form of a virus that contains the genome, allows for intracellular travel, virion
a virus infection is ______________ the entry of a virus/virus genome into a suitable cell
a virus (can/cannot) respond to environment until entry into cell a virus CANNOT respond until entry into a cell
the capsid of a virus contains _________________ the virus genome
the capsid of a virus is composed of small proteins called capsomeres
a naked capsid is a capsid that does not have any layers and infects bacteria
describe the anatomy of a capsid with an envelope the envelope is made of a phospholipid bilayer (similar to an animal cell plasma membrane) and a nucleocapsid which includes the nucleic acid and the capsid
what is the main purpose of the capsid to protect the genome
(some/all) viruses contain virus-specific enzymes SOME viruses contain virus-specific enzymes
name the two different "cycles" that a virus goes through after an infection 1) virulent (lytic) and 2) lysogenic
the (Lytic/Lysogenic) cycle the virus replicates and destroys the host LYTIC cycle the virus replicates and destroys the host
which virus cycle does the virus redirect the cell metabolism redirect to replicate and grow more virus genomes and virions lytic cycle redirects the cell metabolism to replicate itself and grow more viruses
in what viral cycle does the virus cause the cell to lyse and releasing new viruses lytic cycle the virus causes the cell to lyse and release new viruses
in the lysogenetic cycle the host cell (is/is not) destroyed in the lysogenic cycle the host cell IS NOT destroyed
how does the lysogenic virus infection alter the cell in lysogenetic viruses, the virus genome genetically alters the host cell
list the types of genomes that are found in capsids of viruses single stranded RNA, single stranded DNA, double stranded RNA, double stranded DNA
in viruses, the genome is (linear, circular, both) the virus genome can be BOTH linear and circular
a plus sense is the viral mRNA that will be directly translated
a minus sense is complementary base sequence to viral mRNA
viruses that only infect bacteria are called bacteriophages
why are bacteriophages important, they are used to study microbiology
in a virion, the nucleic acid is always surrounded by the capsid
the capsid is composed of _____________________ arranged in precise pattern capsomeres
Describe the structure of the Tobacco Mosaic Virus (TMV) single stranded RNA, wound in a helix, capsomeres jutting out of the RNA
when virion assembly is spontaneous self-assembly
name and describe the two types of virion structure rod (symmetrical about an axis formed by a helix), spherical (radial symmetry created by icosohedral)
generally speaking, an icosohedral (spherical symmetrical) virus has _______________ triangles, __________________ verticies, and ____, ____, ______ axes 20 triangles, 12 verticies, and 2, 3, 5 axes
why is the icosohedral the most common arrangement for virion because it is the mores efficient arrangement with the smallest number of capsomeres per face
describe the shape of the T4 virion body shape includes a head and a helical tail
describe the shape of enveloped viruses a nucleocapsid surrounded by a lipoprotien membrane
envelope viruses primarily infect (animal/bacterial) cells envelope viruses primarily infect ANIMAL cells
what is the mechanism for envelope virus infection the envelope attaches to the plasma membrane and the nucleocapsid is let into the cell
the envelope (does/does not) assist with the virion exiting lysed cells an envelope DOES assist with a virus leaving the lysed cell
in the case of an infection, the penetration of an envelope into a cell is determined by the biochemistry of the envelope determines what type of cell the virus can penetrate
there (are/are not) virus-specific envelopes there ARE virus-specific envelopes
viruses are metabolically inert meaning... viruses do no carry out metabolic processes
how do viral enzymes play a role in infections help to lyse the cell wall and aid in the release of the virus from the host
name the enzyme in the influenza virus that is known for releasing a flu virion from the host cell neurominidase
retroviruses are only known to infect retroviruses only infect ANIMAL cells
retroviruses only use __________________________________ enzymes to replicate DNA intermediates RNA-Dependent DNA polymerase (reverse transcriptase)
how are virus infections in Bacteria/Archaea different from virus infections in eukaryotes viruses inject their nucleic acid into the host cell and only the genome enters, while in Eukaryotes the entire Virion enters the cell
a _______________ cell is a cell that supports complete replication cycle permissive
what are the five steps in virus - infection 1) attachment (absorbtion) , 2) penetration (entry/injection), 3) synthesis, 4) assembly and packing, 5) release
_______________________ is the amount of time for a virion's number to increase in a culture medium one-step growth curve
at what point is the virion number considered to have increased when the cell bursts
name the two phases in the one-step growth curve 1) eclipse phase and 2) maturation phase
what characteristics are part of the eclipse phase the viral genome and proteins being replicated/transplanted and the virion is no longer available to infect another cell
in what phase of the growth cycle is characterized by new viruses being synthesized and packed into new capsids, while the number of new virions drastically increase. however, their number is not detected because they are inside the cell maturation phase
what is burst size the number of mature virions release after a cell lyses
in the attachment phase of a viral infection viruses can attack (any and every cell/only specific cells) in the attachment phases, viruses can attack ONLY SPECIFIC CELLS
viruses can only attack specific cells during an infections, why viruses will only infect the cells which carry specific receptors
if a mutation causes a change in a specific viral receptor on a cell, what will happen the virus will be unable to infect that cell
what are cell receptors made out of macromolecules (protiens, lipids, carbs)
what happens once a virus successfully attaches to a receptor on a cell after binding to a receptor, changes will occur in the virion and the host cell
the virion attaches to the host cell, changes then occur in both virion and host cell, then what happens. penetration
in Bacteria and Archaea, the penetration step is characterized by the genome of the virus being injected into the cytoplasm eventually resulting in genome and protein replication
the genome for Bacteriophage T4 is double stranded DNA (folded)
describe the virion shape of Bacteriophage T4 series of tail fibers and tail pins attached to a icosohedral head
the point(s of attachment for a Bacteriophage T4 is/are) tail fibers and tail pin
the DNA genome of the Bacteriophage T4 enters the cytoplasm via what structure on its virion tail tube
what are two built-in mechanisms that cells have for destroying virus genomes Toxin-Antitoxin modules and Antiviral system (CRISPR)
what is the function of restriction endonuclease an enzymes that cleaves DNA at specific sites
what is the name of the mechanism in Bacteria and Archaea that uses restriction endonuclease to cleave virus DNA out of normal DNA Restriction
how does host use viral DNA to make it into its own genome modification
how is modification done methylation of viral nucleotides by the host cell
what is a protective mechanism of T4 substitutes base 5-hydroxymethycytosine in place of cytosine
name the two enzymes that are produced after T4 enters into a permissive cell T4 primase and helicase
what is circular permutation every copy of the virus consists the *exact same* set of genes
a viral genom of DNA that is duplicated on both ends of the DNA molecule terminally redundant
what is a concatemer in DNA several genomic unites that are recombined end-to-end
what is headfull packing T4 DNA packed into a capsid....fills up the capsid
________________________ begins the process of new virion formation Transcription + Translation
_______________ begins almost immediately after a virus invades a cell Transcription
name the three major sets of proteins (named in order of appearance) - early proteins - middle proteins - late protiens
what is the function of early proteins in T4 synthesis and glucosylation in 5-hydroxymethylcytosine, replisome, produce copies of phage-specific genome, modify host RNA polymerase
Middle and late proteins are responsible for additional RNA polymerase and modifying proteins, producing structural + release proteins (head and tail proteins)
what do T4 modifications to host RNA do hos RNA then only recognize phage promoters
what shuts down normal cell transcription during an infection the phage encoded antisigma factor
what is the function of anti-sigma factors binds to host RNA polymerase sigma factor, host then starts only transcribing only T4 genes
after anti-sigma factors are bound to RNA polymerase, what happens viral assembly begins
During headful packing, ATP is provided by the host cell
what are the three stages of the headful packing 1) proheads, 2) packing motor, 3) proheads expand
the prohead stage of the headful packing is marked by.... capsid assembly (but it's empty), scaffolding and structural protein building
during the packing morot stage of headful packing... an opening to the prohead, and genome is pumped into the prohead using ATP, the prohead expands, while saffolding is discarded
during the motor discarding phase of the headful packing... the capsid head is sealed
after the cell becomes full of virions the cell.... breaks by osmotic lysing
T4 viruses (always/only sometimes/never) kills it's host T4 viruses ALWAYS kill their hosts
what is a temperate virus a virus that contains a double-stranded DNA, but establishes long-term relationships with their host via lysogeny
what happens to viral DNA when it enters the cell via lysogeny the genome is not transcribed, rather it is replicated in synchrony with host DNA
a cell that harbors virulent DNA is called a lysogen
lysogenic conversion is the growth of a host cell that is controlled by the local environment and nutritional profile
name the two types of lysogeny Lambda and P1
what the the Lambda form of lysogeny the viral genome integrates into the chromosome
what is the P1 form or lysogeny the viral genome exists inside the cell as a plasmid
what is a prophage a viral genome that is living inside a lysogen
during normal replication of a lysogen, what happens to the prophage the prophage will replicate along with the host cell and activation genes remain repressed
what organic structure in a cell is responsible for the maintenance of lysogenic state and inactivated when synthesis is prevented repressive protein
when a stress occurs the host cell then enters into the lytic stage, this is known as induction
what happens during inductions of a lysogen the viral genome is excised from the host DNA (if it's not a plasmid already), then the transcriptions/translations process begins
describe the genome of bacteriophage Lambda it is double stranded DNA which includes a head and a tail
what happens when the Bacteriophage Lambda enters a lytic pathway the genome forms a cancatomeres by rolling circle replication, when attached to host DNA it will straighten out, cell lysis occurs after mature lambda virions are formed
the genome of the Bacteriophage Lambda is integrated to bacteria DNA with the help of ______________ Lambda integrase
what determines which direction the type of cycle that the cell will take after it infects a bacterial cell the accumulation on the type of repressor proteins
name the two main repressor proteins Lambda Repressor (cI protein) and Cro
what happens when there is an accumulation of cI protien represses transcription of Cro (lambda-encoded genes), the virus genome integrates into the host genome
under the (cI protein/Cro) accumulation, the host cell will continue a normal life cycle until triggered by a stressor under the cI PROTEIN accumulation, the host cell will continue a normal life cycle until triggered by a stresser
what is the function of the Cro protien represses the function of cII (which controls cI activation) and forces the Lambda to travel to the lytic pathway
in regards to the virus genome entering into the host cell, what are the differences between animals and bacteria animal cells will engulf the entire virion, bacterial virion will "inject" their virion
what is the main difference between site of replication in animal cells and bacterial cells in animal cells site of replication is in the nucleus
in (all/animal/bacterial) cells, viruses bind to receptors in order to initiate infection. in ALL cells viruses bind to receptors in order to initiate an infection
explain why animals can get a virus in some areas of their body but not others. animals have different systems, the cells in each system have different receptors. this is why you can only get a cold in your respiratory system
how does a virion enter an animal cell endocytosis or the nuclear envelope fuses with the cytoplasmic membrane
if the viral genome is DNA, what happens after the virion enters into the host cell the DNA genome passes through the nuclear envelope for replication
if the viral genome is composed of RNA, what happens after the virion enters host cytoplasm the RNA genome is replicated/converted to DNA within the nucleocapsid
what are the four possible outcomes when a virus infects an animal 1) virulent infection, 2) latent infection, 3) persistent infection, 4) transformation
what type of virus infects an animal cell includes a lytic cycle virulent infection
of the four types of infections in animal cells, which one is the most common virulent infections are the most common types
in animals cells,
Created by: kandriot
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