Ch. 13 - General Characteristics of Viruses

went to different strains of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in __________. (13.5)

antigenic shift

Viruses that infect bacteria are called ______. (introduction)

bacteriophages or phages

Animal viruses that do not have an envelope can only enter their host cell by ____________. (13.5)

endocytosis

T/F: it is easier to cultivate animal viruses than bacteriophages. (13.8)

flase

Rank the following by size, from smallest to largest, starting with the smallest at the top. (13.1)

1. Viruses 2. Bacteria 3. Human cells

The study of viruses is important because ________ . (introduction)

- bacteriophages play a significant ecological role in reducing bacterial populations in nature - viruses can be a vehicle for horizontal gene transfer in bacteria - there are many medically important viruses that cause disease

Bacteriophages play a fundamental role in which type of horizontal gene transfer? (13.3)

Transduction

T/F: viral particles can be shared from a host in feces, urine, gential secretions, blood, or muscus and saliva released from the respiratory tract during coughing or sneezing, allowing for transmission to a new host. (13.1)

True

Which of the following statements about viruses nucleic acid is true? (13.1)

Viruses contain either DNA or RNA.

During the ______ or maturation step is viral replication, capsids and genetic material are packaged into virions. (13.5)

assembly.

In the lytic cycle of the T4 page, lysozyme degrades a portion of the bacterial ______ . (13.2)

cell wall

In the lysogenized bacterium, ___________ of the prophage results in a lytic infection. (13.2)

excision

____________ transduction is the result of packaging errors during the assembly stage of phage replication. (13.3)

generalized

The protein receptor molecules of a host cell to which viruses attach by their spikes are typically ________ . (13.5)

glycoproteins

All of the following are required for synthesis of new virus particles in a host cell except ____________ . (13.5)

homologous recombination

A viral infection in which the viral genome is integrated into an animal host cell chromosome, yet can reactivate to cause a productive infection, is categorized as a(n) ________. (13.6)

latent

A __________ tumor is one that can metastasize or spread to nearby tissue. (13.7)

malignant

in envelope viruses, sandwiched between the nucleocapsid and the envelope is the _________ . (13.1)

matrix protein

One of the early proteins expressed in the T4 lytic cyle is an enzyme called a ___________ that degrades the bacterial DNA. (13.2)

nuclease

Most animal DNA viruses will replicate within the host cell's ____________ . (13.5)

nucleus.

The stage of viral multiplication at which budding occurs is _______ . (13.5)

release

A virus acquired by inhalation would be called a(n) ________. (13.1)

respiratory virus

HIV is described as a ____ because it uses reverse transcriptase to make a DNA copy from its RNA genome. (13.5)

retovirus.

Reassortment of gene segments that encode viral surface proteins that are recognized by the immune system can result in a loss of the immune system's ability to recognize and respond to the virus. this phenomenon is called antigenic ___________ . (13.5)

shift.

Viral infections in plants can cause diseases ________. (13.9)

that are exonomically devastating

which is most important for attachment of a virus to a host cell? (13.5)

viral specificity for host receptors

Replicases are ___________ polymerase. (13.5) percent

RNA- dependent RNA.

Reverse transcriptase is a(n) __________ polymerase. (13.5)

RNA-dependent DNA

The process by which a virus is taken up by a host cell as a result of the host cells cytoplasmic membrane surrounds the virion to form a vesicle is called _______. (13.5)

endocytosis

T/F: Bacteriophages are important medically because they can be used to prevent the growth of food-contaminating pathogens. (introduction)

True

symptoms of acute viral diseases result from __________. (13.6)

- host tissue damage - host immune response

Viruses are challenging to study because _________ . (introduction)

- they are obligate intracellular parasites - they can only be seen using an electron microscope

Specialized transduction ____________. (13.3)

- results from errors in excision of the prophage. - transfers phage DNA and adjacent host genes. - produces defective phage particles.

The viral genome is protected from the environment by a protein shell called the _________ . (13.1)

capsid

Some pathogenic bacteria produce toxins that are encoded on prophage DNA, and these are examples of ________ conversion. (13.2)

lysogenic

___________ infectious remain for years, or even the lifetime of the host, sometimes without any symptoms. (13.6)

persistent

unlike animal viruses that attach to specific receptors in order to gain entry into the cell, _________ viruses can gain entry into a cell through damage in the cell wall. (13.9)

plant

an animal virus genome that has integrated into the genome of the host cell is called a ________. (13.6)

provirus

The enzyme of RNA viruses that lacks proofreading ability and that's makes many mistakes compared to the polymerase of DNA viruses is __________ . (13.5)

replicase.

To maintain the lysogenic state, a ________ protein prevents expression of the gene required for excision. (13.2)

repressor

T/F: tumor tissue can serve as a cell line for viral culture. (13.8)

true

The process by which the viral nucleic acid is released from the protective protein coat is __________ . (13.5)

uncoating.

Which of the following statements about viruses are true? (13.1)

- Viruses contain RNA or DNA but not both - The viral capsid is composed of protein

What are the two major categories of viral imfections? (13.6)

- acute - persistent

what mechanism do newly assembled viruses use to leave their host cell? (13.5)

-triggering apoptosis -budding

Which suffix represents a viral family? (13.1)

-virudae

which suffix represents a viral genus? (13.1)

-virus

List the steps of an animal virus infection cycle in the correct order. (13.5)

1. Attachment 2. Penetration and uncoating 3. Sythesis of viral proteins and replication of the genome. 4. Assemby 5. Release

Im which phase of the T4 phage lytic cycle are new phage particles put together? (13.2)

Assembly

The phage attaches to specific receptors on the E. Coli cell wall. What stage of the T4 phage lytic cycle does this describe? (13.2)

Attachment

T/F: All virus infections can be clearly categorized as either acute or persistent. (13.6)

False

T/F: envelope and non-envelope viruses all mature fully in the cytoplasm of the host cell. (13.5)

False

Which of the following best describes viruses? (introduction)

Infectious agents

Which of the following describes a consequence of lysogeny that could result in human disease? (13.2)

Lysogenic conversion

Which of the following cycles ends with the death (lysis) of the bacterial host cell? (13.2)

Lytic

envelope viruses can derive their envelopes from __________. (13.5)

- certain host organelles - the host cytoplasmic membrane

which of the following are sources of plant viruses? (13.8)

- contaminated pollen - insects - contaminated seeds - soil

Which of the following methods can be used to quanify animal viruses? (13.8)

- direct count - plaque assay - quantal assay - hemagglutination

Which are the two main criteria used in classifying viruses? (13.1)

- host range (host they infect) - genome structure

T/F: envelope viruses enter the host cell by endocytosis only, well non-envelope viruses can enter the Hosell by fusion or endocytosis. (13.5)

False

T/F: Lysogens are more susceptible to reinfection by the same type of phage. (13.2)

False (Lysogens are immune to superinfections)

A __________ shaped virus appears cylindrical under an electron microscope, but the capsomeres are arranged in a helix, smiliar to sprial stair case. (13.1)

Helical

Which of the following directs the incorporation of the phage DNA into a bacterial chromosome? (13.2)

Integrase

Which of the following about classifying viruses is FALSE? (13.1)

It is not as impor as classifying organisms since they are not living entities.

The number of phage particles particles released from a host cell is the _______ . (13.2)

burst size

Which of the following describe a type of relationship that bacteriophages can have with their host? (13.2)

- productive lytic infection - latent infection where host cell genotype is changed

regarding animal viruses, which of the following statements are true? (13.5)

- viruses use their spikes to attach to host cell receptors. - some viruses require more than one host receptor for attachment. - Blocking a host receptor with a drug would prevent a virus from infecting that cell.

The replication strategies of animal viruses can be divided into three general categories: those used by __________ viruses, __________ viruses, and reverse transcribing viruses. (13.5)

-DNA -RNA

The enteric viruses are a group of taxonomically unrelated viruses that are grouped together for which of the following reasons? (13.1)

They are transmitted by the fecal-oral route.

Although live animals and fertilized chicken eggs have been used to cultivate animal viruses in the past these have been largely replaced by __________ culture. (13.8)

cell

Tumors are abnormal growths that result from a malfunction in the regulation of _________. (13.7)

cell growth

if a sample contains a high enough concentration of viruses a(n) __________ microscope can be used to directly count the number of viral particles in a suspension. (13.8)

electron

following generalized transduction, DNA from the donor so maybe integrated into the host cell chromosome by __________ recombination. (13.3)

homologous

Lysogeny is best described as ________. (13.2)

integration of the viral genome into the host chromosome

The physical rupture of a cell is termed _______ . (13.2)

lysis

_____________ transduction is the result of excision errors made as template phages transition from lysogenic to a lytic cycle. (13.3)

specialized

The viral proteins that sticks out from either the lipid bilayer of envelope viruses or the capsid of non-envelope viruses, and attached to the host cells are ________ . (13.1)

spikes

before envelope viruses bud from a host cell, specific viral proteins insert into the host membrane. these proteins become __________. (13.5)

viral spikes

The most common method used today in the cultivation of animal viruses is _________. (13.8)

tissue culture m