Chapter 13, Exam Two Flashcards
Contain a single type of nucleic acid. Contain a protein coat. Multiply synthesizing machinery of the cell. Synthesis of specialized structures that can transfer the viral nucleic acid to other cells.
Viruses
Of a virus, is the spectrum of host cells the virus can infect.
Host range
Viruses are sensitive to interferon true or false
True
Viruses possess both DNA and RNA true or false
False
Narrow host range and ability to kill their host cells
Idea of phage therapy
Using bacteriophage to treat bacterial infections
Phage therapy
Viruses that may selectively in fact and kill tumor cells or cause any response against tumor cells
Oncolytic viruses
A complete, fully developed, infectious viral particle composed of nucleic acid and surrounded by a protein coat outside a host cell
Viron
nucleic acid of a virus is protected by a protein coat
Capsid
Protein subunits of capsid
Capsomeres
Combination of lipids, proteins, and carbohydrates that cover a Capsid.
Envelope
Host cell’s plasma membrane coating animal virus. Extrusion process. May contain proteins determined by the viral nucleic acid and materials derived from normal host cell components.
Viral envelope
Carbohydrate – protein complexes that project from the surface of the viral envelope
Spikes
The capsid of this virus protects the nucleic acid from nuclease enzymes in biological fluids and promotes the viruses attachment to susceptible host cells
Non-enveloped to viruses
Helical viruses
Ebola and rabies
Polyhedral viruses
Icosahedron, 20 triangular faces and 12 corners
Roughly spherical, enveloped helical or enveloped polyhedral viruses
Enveloped viruses
Bacteriophage, structures such as the capsid, but tail sheath, tail fibers, base plate, and pin
Complex viruses
The international committee on taxonomy of viruses group viruses into families based on what?
Genomics and structure
A bacteriophage sample is mixed with host bacteria and melted agar. clearings or plaques are visible against a lawn of bacterial growth.
Plaque method
Each plaque corresponds to a single virus in the initial suspension. Concentrations of viral suspensions measured by the number of plaques are usually expressed in terms of…
Plaque forming unit PFu
Require living host cells in order to multiply
Intra-cellular parasites
When two or more strains of the virus combined to form a new subtype having a mixture of surface antigens of two or more original strains
Antigenic shift
Host for many animal viruses. A hole is drilled in the shell of an embryonated egg, and a viral suspension is injected into the egg’s fluid. Viral growth is signaled by the death of the embryo by embryo cell damage, or the formation of typical pox or lesions in the egg membranes. Vaccinations may have egg proteins.
Embryonated egg
Cells grown in culture media in a laboratory. Cell lines are started by treating a slice of animal tissue with enzymes that separate individual cells. Cells are suspended in a solution. Normal cells and here to glass or plastic and produce a monolayer.
Cell culture
Cell deterioration in cell culture is called
Cytopathic effect
Derived from tissue slices tending to die only after a few generations
Primary cell lines
Develops from human embryos, can be maintained for about 100 generations, widely used for culturing viruses that require a human host.
Diploid cell Lines
Transformed cancer cells that can be maintained through an indefinite number of generations, sometimes called immortal
Continuous cell lines
Serological method most used as a means of identification. Virus is detected and identified by it’s reaction with antibodies.
Western blotting
By infecting every cell in a culture and then testing the culture medium and cells for virions and viral proteins and nucleic acids. Growth curve looks like a single peak.
One step growth curve
Bacterial phage alternative mechanism/ lifecycle where lysis and death of the host cell occur
Lytic cycle
Bacteriophage can multiply by this cycle. Where the host cell remains alive.
Lysogenic cycle
Attachment, penetration, biosynthesis, maturation, and release.
Lytic cycle of t-even phage
Where a virus attaches to a complementary receptor site on the bacterial cell
Attachment, lytic cycle
Where a T even cell injects it’s nucleic acid into bacterium using phage lysozyme. Phage particle functions like a hypodermic syringe.
Penetration, Lytic cycle
Breaks down a portion of the bacterial cell wall
Phage lysozyme
Host protein synthesis is stopped by virus induced degradation of the host DNA, viral proteins that interfere with transcription, or the repression of translation. Initially, the phage uses the host cells nucleotides and several of it’s enzymes to synthesize many copies of phage DNA. Biosynthesis of viral proteins begins. The host cells ribosomes, enzymes, and amino acids are used for translation. Late messages are translated into phage capsid proteins.
Biosynthesis, lytic cycle
Multiplication is complete, infective virions are not present yet
Eclipse period
Phase in which viral component assemble into viral particles spontaneously
Maturation, lytic cycle
Virons are released from the host cell. Lysis due to lysozyme.
Release, lytic cycle
Some viruses don’t cause life and death of the host cell when they multiply
Temperate phages /T even bacteriophages
DNA is incorporated into host cells DNA, phage remains latent
Lysogeny
Inserted phage DNA, repressed by to repressor proteins that are the products of phage genes
Prophage
Phage attaches to host cell and injects DNA. Phage DNA circularizes is and enters the lysogenic cycle. Phage DNA integrates with in the bacterial chromosome by recombination becoming a prophage. Lysogenic bacterium reproduces normally. Occasionally the prophage may excise from the bacterial chromosome buy another recombination event initiating a lytic cycle.
Lysogenic cycle, bacteriophage lambda and E. coli
- Lysogenic cells are immune to reinfection by the same phage. 2. Phage conversion- the host cell may exhibit new properties. 3. The result of Lysogeny is that it makes specialized transduction possible.
Three important results of lysogeny
Bacterial genes and prophage can be picked up in a phage coat and transferred to another bacterium
Specialized transduction
Prophage exist in galactose – using host
Specialized transduction step one
Phage genome exercises, caring with it the adjacent gal gene from the host
Specialized transduction step two
Phage matures and cell lysis, releasing phage carrying gal Gene
Specialized transduction step three
Phage infects a cell that cannot utilize the lactose (lacking gal Gene)
Specialized transduction step four
Along with the prophage the bacterial gal gene becomes integrated into the new host DNA
Specialized transduction step five
Lysogenic cell can now metabolize galactose
Specialized transduction step six
Attachment to complementary receptor sites on the host cell surface results in The plasma membrane continuously folding InWard to form vesicles
Receptor – mediated endocytosis
When the viral envelope fuses with the plasma membrane and releases the capsid into the cells cytoplasm
Fusion
Separation of the viral nucleic acid from its protein coat sometimes caused by the action of lysosomal enzymes of the host cell
Uncoating
Copies messenger RNA to make viral DNA
Reverse transcriptase
Viral enzymes replicate DNA in the _______ of the host cell
Nucleus
Viral proteins and the capsid are synthesized in the_________ which then migrate into the nucleus and join with the newly synthesized DNA to form _____. These are transported along the endoplasmic reticulum to the host’s cell membrane for release.
Cytoplasm, virons
___________ multiply in the host cells cytoplasm.
RNA viruses (Example: Picornaviridae)
This enzyme catalyzes the synthesis of another strand of RNA which is complementary in sequence to the original infecting strand
Rna – dependent RNA polymerase
RNA within the virion is Called the ________. It can act as messenger RNA.
Sense strand (plus strand)
To principal proteins are translated from single-stranded viral RNA
One inhibits the host cells synthesis of RNA and the other is an RNA-dependent RNA polymerase, which makes an anti-sense strand (minus strand).
DNA containing viruses replicate their DNA in the nucleus of the host cell by using what?
Viral enzymes
DNA contain viruses synthesize there capsid and other proteins in the cytoplasm using what? Capsid proteins reenter the __________ where virons mature.
Host cell enzymes
DNA contain viruses, virions are transported along the?
endoplasmic reticulum
In most DNA viruses early transcription is carried out with?
The host’s transcriptase
RNA viruses multiply in the host cells
Cytoplasm
This enzyme isn’t encoded in any cells genome. Viral genes cause the enzyme to be made by a host cell. The enzyme catalyzes the synthesis of another strand of RNA.
RNA dependent RNA polymerase
Plus strands (sense strands) serve as Messenger RNA and are incorporated into __________ proteins as the viral genome.
Capsid
In RNA containing viruses, the - strand may be incorporated into capsid protein, but The _________ only codes for proteins.
Plus strand
DNA containing viruses replicate their DNA in the nucleus of the host cell by using what?
Viral enzymes
DNA contain viruses synthesize there capsid and other proteins in the cytoplasm using what? Capsid proteins reenter the __________ where virons mature.
Host cell enzymes
DNA contain viruses, virions are transported along the?
endoplasmic reticulum
In most DNA viruses early transcription is carried out with?
The host’s transcriptase
RNA viruses multiply in the host cells
Cytoplasm
This enzyme isn’t encoded in any cells genome. Viral genes cause the enzyme to be made by a host cell. The enzyme catalyzes the synthesis of another strand of RNA.
RNA dependent RNA polymerase
Plus strands (sense strands) serve as Messenger RNA and are incorporated into __________ proteins as the viral genome.
Capsid
In RNA containing viruses, the - strand may be incorporated into capsid protein, but The _________ only codes for proteins.
Plus strand
These viruses carry reverse transcriptase which uses the viral RNA as a template to produce complementary double-stranded DNA
Retroviruses
The retroviral __________ unlike a prophage never comes out of the chromosome. HIV
Provirus
Retrovirus entered by fusion between attachments spikes and the host cell receptors (two identical plus strands of RNA)
Step 1, retrovirus multiplication
Uncoating releases the two viral RNA strands and the viral enzymes reverse transcriptase, integrase, and protease.
Step two retrovirus multiplication
Reverse transcriptase copies viral RNA to produce double-stranded DNA
Step three retroviral multiplication
The new viral DNA is transported into the cells nucleus where is integrated into the cells chromosomes as a provirus by viral integrase. The provirus may be replicated when the host cell replicates.
Step four retroviral multiplication
Transcription of the provirus may occur producing RNA for new retrovirus genomes and RNA that encodes the retrovirus capsid, enzymes, and envelope proteins.
Step five retroviral multiplication
Viral proteins are processed by viral protease; some of the viral proteins are moved to the host plasma membrane
Step six of retroviral multiplication
Mature retrovirus leaves the host cell acquiring an envelope and attachments spikes as it buds out
Seven of retroviral multiplication
Capsids are enclosed by an envelope consisting of envelope protein encoded by viral genes and incorporated into the plasma membrane of the host cell. The envelope lipids and carbohydrates are encoded by the host cell genes. Does not kill the host cell.
Budding In retroviral multiplication
First, most of the particles of some viruses infect cells but do not cause cancer. second, cancer might not develop until long after the viral infection. Third, cancers even those caused by viruses don’t seem to be contagious as viral diseases usually are.
The viral cause of cancer can often go unrecognized
Cancer inducing genes carried by viruses are actually derived from animal cells
OnCogenes
Virus is capable of inducing tumors and animals. Their genetic material integrates into the host cells DNA and replicates along with the host cells chromosome.
Oncoviruses
Properties that are distinct from the properties of an infected cells or from infected cells that don’t form tumors
Transformation
Many tumor cells contain a virus specific antigen on their cell surface
Tumor specific transplantation antigen (TsTA)
Antigen in the nucleus
T antigen
Among the RNA viruses, the only oncoviruses that causes cancer
Retroviridae
Infect and lyse cancer cells
Oncolytic viruses
A virus can remain in equilibrium with the hose and not actually produce disease for a long period
Latent infection
Detectable infectious virus gradually build up over a long period
Persistent viral infection
Proteinaceous infectious particle
Prion
Short pieces of naked are only 3 to 400 nucleotides long with no protein coat
Viroids
