exam1 effect of virus on host Flashcards by Cheryl Hausle

In lysis, what happens to the host cell?

viral replication is complete.

host cell is destroyed and new virions released

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what is apoptosis?

programmed cell death. host activates as last resort to eliminate viral factories before progeny production is complete

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Which of the following are possible effect the virus will have on the host cell?

a. cytocidal
b. non-cytocidal
c. cell tranformation
d. all of the above

d. all of the above

cytocidal - leads to cells death
non-cytocidal - leads to persistent infection
cell transformation - tumor cells

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What is cytopathic effect?

CE is the damage or morphological changes to host cells during virus invasion

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What is the primary effect of cytopathic effect?

a. metabolic needs of the virus
b. physical morphological changes
c. both a and b
d. physiological needs of the virus

b. physical morphological changes

primary effect is induced by viral replication and viral proteins toxic to host cells

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What is secondary effect of cytopathic effect?

a. metabolic needs of the virus
b. physical morphological changes
c. both a and b
d. physiological needs of the virus

a. metabolic needs of the virus

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T/F Cytopathic effect can result in : complete, subtotal, and focal destruction of cells.

true

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Which of the following is an example of virus using complete destruction of cells due to cytopathic effect?

a. enteroviruses
b. herpesviruses
c. poxviruses
d. togaviruses

this is the most severe form of CPE. all cells in monolayer rapidly shrink, become dense, and detach from the glass within 72 hours

a. enteroviruses

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Which of the following is an example of virus using subtotal destruction of cells due to cytopathic effect?

a. enteroviruses
b. herpesviruses
c. poxviruses
d. togaviruses

this CPE consists of detachment/death of some but not all of the cells in the monolayer

d. togaviruses

as well as some picornaviruses, and some paramyxoviruses

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Which of the following is an example of virus using subtotal destruction of cells due to cytopathic effect?

a. paramyxoviruses
b. herpesviruses
c. poxviruses
d. both b and c

This CPE produces localized areas of infection

d. both b and c
herpesviruses
poxviruses

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Define Pyknosis.

a. cell nucleus is clumping/shrinking
b. cell nucleus is fragmenting
c. cell nucleus is fading

a. cell nucleus is clumping/shrinking

clumping of chromosomes, hyperchromatism

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Which of the following is not an effect of Cytopathic effect?

a. cell lysis
b. cell elongation
c. cell detachment
d. swelling and clumping

b. cell elongation

cells become rounded.

vacuoles in cytoplasm
inclusion bodies
syncytium formation
antigenic changes in cell membrane

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Define syncytium

multinucleated cell

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cell fusion involves the fusion of the plasma membrane of at least how many cells to produce an enlarged cell?

a. 2
b. 3
c. 4
d. 5

c. 4

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T/F multinucleated cells that form as a result of cell fusion are prone to premature cell death.

True

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Enveloped viruses specifically direct the insertion of their surface glycoproteins, into the host cell ____ as part of their budding process.

a. nucleus
b. cytoplasm
c. cell membrane

c. cell membrane

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T/F Synsytia formation may not be the only detectable CPE of some paramyxoviruses

FALSE

Sysytia formation may BE THE ONLY detectable CPE of some paramyxoviruses

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What are inclusion bodies?

abnormal structure in a cell nucleus or cytoplasm or both. such as aggregates of proteins, having characteristic staining properties and associated with certain viral infections.
help to ID certain viral infection

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Inclusion bodies can

a. result from degenerative changes in the cell
b. crystalline aggregates of virions
c. accumulations of viral components
d. all of the above

d. all of the above

a. result from degenerative changes in the cell
ex: owl’s eye inclusion bodies
b. crystalline aggregates of virions
ex: adenovirus inclusion bodies
c. accumulations of viral components
ex: negri bodies

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T/F inculsion bodies in host cell during viral infection stain only acidophilic.

False

inculsion bodies in host cell during viral infection stain BOTH acidophilic OR basophilic

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What is acidophilic staining?

affinity for acid dyes, such as eosin. appear pink

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What is basophilic staining?

affinity for basic dyes such as hematoxylin. appear purple/blueish

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T/F In inhibition of host-cell nucleic acid synthesis, large DNA viruses produce enzymes that may degrade cellular DNA of the host.

True

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T/F Inhibition of Host-cell RNA transcription is a direct consequence of viral effect on host-cell protein synthesis that decreases availability of transcription factors required for RNA polymerase activity.

FALSE
Inhibition of Host-cell RNA transcription is a INDIRECT consequence of viral effect on host-cell protein synthesis that decreases availability of transcription factors required for RNA polymerase activity.

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What happens in the inhibition of host-cell synthesis?

the virus synthesizes large numbers of mRNA and they out compete the host mRNA. some viruses cause lysosomes to release their hydrolytic enzymes, and destroy host cell.

T/F In apoptotic pathways, once activated, caspases are responsible for degradation of the cell's own DNA and proteins

True

What is the Intrinsic (mitochondrial) pathway?

activated as a result of increased permeability of mitochondrial membranes subsequent to cell injury

What is the extrinsic (death receptor) pathway?

activated by engagement of specific cell-membrane receptors, which are members of the TNF receptor family. thus binding the cytokine TNF to its cellular receptor can trigger apoptosis.

T/F cytotoxic T lymphocytes and NK cells can initiate apoptosis of virus-infected target cell.

True utilizing performed mediators such as perforin and granzyme that directly activate caspases in the target cell.

Membrane fusion occurs in : a. eveloped viruses only a. noneveloped viruses only a. eveloped viruses and nonenveloped viruses

a. eveloped viruses only

T/F glycoproteins on cell surface are not antigenic, and therefore do not become a target of the immune system of the host.

FALSE | glycoproteins on cell surface ARE antigenic, and therefore DO become a target of the immune system of the host.

T/F non-cytocidal viruses cause immediate death of cells in which they replicate

FALSE non-cytocidal viruses DO NOT cause immediate death of cells in which they replicate. remember cytocidal means killing of the cell. non-cytocidal would be NOT killing the cell

T/F Non-cytocidal changes often lead to slow progressive changes that ultimately lead to cell death

True. often cause persistent infections and can produce important changes in their host affecting regulatory, homeostatic, and metabolic functions.

T/F non-cytocidal changes always have effect on overall function of the host cell.

FALSE non-cytocidal changes DO NOT always have effect on overall function of the host cell. in host animals, cell replacement occurs so rapidly in most organs/tissues that the slow fallout of cells as a result of persistent infection may have no effect on overall function.

Define cell transformation.

changing of normal cell into a cancer cell.

Define Neoplasia

descriptive term to denote abnormal tissue overgrowth that may be either localized or disseminated.

What is Oncology?

study of neoplasia and neoplasm

What is a benign neoplasm? a. growth that is locally invasive and may spread to other parts of body. b. growth produced by abnormal cells proliferation that stay localized.

b. growth produced by abnormal cells proliferation that stay localized.

What is a malignant neoplasm? a. growth that is locally invasive and may spread to other parts of body. b. growth produced by abnormal cells proliferation that stay localized.

a. growth that is locally invasive and may spread to other parts of body (metastasis)

Oncogenic Viruses : a. cause of give increased growth b. cause or give rise to tumors

b. cause or give rise to tumors

T/F neoplasms (tumors) arise as a consequence of regulated growth of cells derived from a single cells, genetically altered progenitor cell.

FALSE neoplasms (tumors) arise as a consequence of DYSregulated growth of cells derived from a single cells, genetically altered progenitor cell.

What is metastasis?

spread of cancer cells from the part of the body where it started to other parts of the body.

proto-oncogenes : a. encode proteins that function in normal cellular growth and differentiation a. encode proteins that function in irregular cellular growth and differentiation

a. encode proteins that function in normal cellular growth and differentiation these are genes that normally help the cells to grow

What is the role of Tumor suppressor genes?

Keep cell division in check. | encode proteins that regulate and inhibit uncontrolled growth.

A mutation in which of the following can lead to cancer? a. proto-oncogene b. tumor suppressor gene C. all of the above

C. all of the above

What is the signal transduction cascade?

the activation of one protein to activate another to eventually lead to mitosis (cell division)

Which of the following does NOT cause proto-oncogenes to become oncogenes (cancerous phenotypes)? a. chemicals b. NK cells c. UV rays d. virus

b. NK cells

T/F proto-oncogenes can mutate to become oncoproteins that function in an unregulated manner

True

T/F receptors encoded by oncogenes require regulatory steps to be activated.

FALSE | receptors encoded by oncogenes DO NOT require regulatory steps to be activated.

``` Which of the following is a Tumor Suppresor proteins? a. Bb b. Rb C. Gg d. Mm ```

b. Rb retinoblastoma protein

the Rb protein is phosphorylated by which enzyme? a. CDKs b. CDPs c. CDLs d. CDXs

a. CDKs Cyclin Dependent Kinases

T/F E5F transcription factor is necessary for the expression of a number of cell-cycle-specific genes.

FALSE --> E2F

What is the role of Un-phosphorylated Rb? a. bind to trascription factor E2F, preventing it's activity b. promote cell division c. inhibit cell division d. both a and c

d. both a and c inhibit cell division to proccess from G1 to S phase

T/F phosphorylated Rb can bind E2F

FALSE phosphorylated Rb CANNOT bind E2F. this release of E2F from inhibition allows cell division to proceed.

Loss of normal Rb function leads to : a. control over cell cycle b. loss of control over the cell cycle

b. loss of control over the cell cycle

T/F P16 can block CDK

True. P16 is a tumor suppressor protein. P16 blocks CDK so CDK cannot phosphorylate Rb. Then Rb is free to bind and inhibit action of E2F

Which of the following are NOT tumor-suppressor genes? a. P26 b. p16 c. Rb

a. P26 P16 blocks CDK - so it cannot phosphorylate Rb. Rb binds to E2F to inhibit cell division

What does p53 protein do?

p53 activated the DNA repair system and stops the cell at the G1 checkpoint, before DNA replication

T/F oncogenic viruses generally have a DNA genome or generate a DNA provirus prior to infection.

FALSE | oncogenic viruses generally have a DNA genome or generate a DNA provirus AFTER infection.

T/F the genome of oncogenic viruses never integrate into host genome.

TRUE but they do have autonomous replicating system.

Which of the following are the MOST important oncogenic viruses in animals? a. poxvirus b. herpesvirus c. rotovirus d. retrovirus

d. retrovirus

Name the two ways that DNA tumor viruses interact with cells.

1. productive infection - virus completes its replication cycle, resulting in cell lysis. 2. Transformation - virus transforms cell without completing its replication cycle

Oncogenic Papillomaviruses produce what on the skin and mucous membranes of most animals? a. rashes b. abrasions c. warts d. pigmentation

c. warts warts are benign neoplasms that are hyperplastic epithelial outgrowths that generally regress spontaneously. however they may become malignant.

In benign warts, papillomavirus DNA is : a. integrated into the host-cell DNA b. not integrated into the host-cell DNA

b. not integrated into the host-cell DNA

In malignant cancers, viral DNA is : a. integrated into the host-cell DNA b. not integrated into the host-cell DNA

a. integrated into the host-cell DNA

T/F Integration dirupts one of the early genes, E2, which is a viral repressor.

True however viral oncogenes (E6 and E7) remain intact and cause the malignant transformation

What proteins do adenovirus E1A and E1B inhibit?

p53 and Rb causing uncontrolled division and growth.

What is the role of papillomavirus (HPV) E7 proteins? a. binds Rb and prevent it from stopping damaged cell growth. b. prevents p53 from making damaged cells commit suicide

a. binds Rb and prevent it from stopping damaged cell growth

What is the role of papillomavirus (HPV) E6 proteins? a. binds Rb and prevent it from stopping damaged cell growth. b. prevents p53 from making damaged cells commit suicide

b. prevents p53 from making damaged cells commit suicide

loss or inhibition of Rb leads to : a. cellular replication b. loss apoptosis in response to viral infection

a. cellular replication

loss or inhibition of p53 leads to : a. cellular replication b. loss apoptosis in response to viral infection

b. loss apoptosis in response to viral infection

JUST FYI : Modified adenovirus produced by Frank McCormick lacks the E1B gene and therefore can only lyse cancer cells in which the cellular p53 gene has been mutated.

seems like a good ghosh fact.

T/F All DNA tumor viruses belong to the family retroviridae

FALSE | All RNA tumor viruses belong to the family retroviridae

T/F Oncogenic RNA viruses have a high rate of muation

True

Remember : c-onc genes/proto-oncogenes are host genes that encode important cell signaling products that regulate normal cell proliferation

it was in bold on pp!

Virus gene do not contain : a. c-onc gene b. p-onc gene c. v-onc gene

c. v-onc gene

Define promoter gene

DNA sequence at which DNA-dep RNA polymerase binds to initiate transcription

Define enhancer gene

transcriptional regulatory sequence located some distance from promoter. it increases the rate of initiation of transcription

Transformation of normal cells to tumor cells are morphologically : a. swollen b. more spindle-shaped c. more rounded

b. more spindle-shaped

what are the 5 types of Tumor Antigens?

1. Differentiation antigens 2. Excessive amounts of normal proteins 3. Mutated proteins 4. Viral coded proteins 5. cancer/testis antigens

Tumor antigens are products of : a. mutated oncogenes b. mutates Tumor suppressor genes c. mutates genes d. all of the above

d. all of the above

T/F the immune system does not recognize these tumor antigens

FALSE the immune system DOSE recognize these tumor antigens. and tries to destroy tumor cells, but they are often not appropriately presented to cells of the immune system, and the cancer cells get through