Chapter 13, Exam Two Flashcards by Jennifer Walrath

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

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Of a virus, is the spectrum of host cells the virus can infect.

Host range

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Viruses are sensitive to interferon true or false

True

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Viruses possess both DNA and RNA true or false

False

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Narrow host range and ability to kill their host cells

Idea of phage therapy

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Using bacteriophage to treat bacterial infections

Phage therapy

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Viruses that may selectively in fact and kill tumor cells or cause any response against tumor cells

Oncolytic viruses

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A complete, fully developed, infectious viral particle composed of nucleic acid and surrounded by a protein coat outside a host cell

Viron

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nucleic acid of a virus is protected by a protein coat

Capsid

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Protein subunits of capsid

Capsomeres

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Combination of lipids, proteins, and carbohydrates that cover a Capsid.

Envelope

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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

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Carbohydrate – protein complexes that project from the surface of the viral envelope

Spikes

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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

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Helical viruses

Ebola and rabies

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Polyhedral viruses

Icosahedron, 20 triangular faces and 12 corners

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Roughly spherical, enveloped helical or enveloped polyhedral viruses

Enveloped viruses

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Bacteriophage, structures such as the capsid, but tail sheath, tail fibers, base plate, and pin

Complex viruses

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The international committee on taxonomy of viruses group viruses into families based on what?

Genomics and structure

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A bacteriophage sample is mixed with host bacteria and melted agar. clearings or plaques are visible against a lawn of bacterial growth.

Plaque method

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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

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Require living host cells in order to multiply

Intra-cellular parasites

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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

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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

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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

1. 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

Chapter 13, Exam Two Flashcards

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