Viruses Overview

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the bacteria (that bacteriophages) infect

are often more pathogenic to humans

Viruses have all the following except ________. A. definite shape B. metabolism C. genes D. the ability to infect host cells E. ultramicroscopic size

B. metabolism

Infectious protein particles are called _______. A. spikes B. prions C. satellite viruses D. viroids E. phages

B. prions

plaques

areas where virus infected cells have been destroyed show up as clear, well defined patches in the cell culture

A virus that undergoes lysogeny is a/an _________. A. T-even phage B. Animal virus C. Temperate phage D. Intemperate phage E. DNA virus

C. Temperate phage

Clear patches in cell cultures that indicate sites of virus infection are called ________. A. Viruses B. Colonies C. Plaques D. Pocks E. Prions F. Viroids

C. plaques

Chronic wasting disease is found in

Canada United States Norway Finland Sweden South Korea

Which of the following is incorrect about prophages? A. Present when the virus is in lysogeny B. Formed when viral DNA enters the bacterial chromosome C. Replicated with host DNA and passed on to progeny D. Cause lysis of host cells E. Occur when temperate phages enter host cells

D. Causes lysis of host cell

When phage nucleic acid is incorporated into the nucleic acid of its host cell and is replicated when the host DNA is replicated, this is considered part of which cycle? A. Lytic cycle B. Cell cycle C. Multiplication cycle D. Lysogenic cycle E. Virulence cycle

D. Lysogenic cycle

bacteriophages translates to

"bacteria eating"

Bovine Spongiform encephalopathy also known as

"mad cow" disease

classical CJD is not related to

"mad cow" disease

archaeal viruses are roughly divided into two categories

1. morphologically and genetically unique to archaea 2. clear structural and genetically homologs to bacteriophages and eukaryotic viruses

Giant viruses (2)

1. pandoravirus 2. mimivirus

examples of oncoviruses

1. papillomaviruses 2.herpesviruses 3. Hepatitis B viruses

three classical scenarios of origin for viruses

1. progressive hypothesis (escaped genes) 2. regressive hypothesis 3. virus first

what controls the number of viruses released by the infected cell

1. size of the virus 2. health of the host cell

____ to ____% of bacterial DNA contains

10-20% viral sequences

Bovine Spongiform Encephalopathy mortality rate

100%

what is Creutzfeldt Jakob Disease mortality rate

100%

poliovirus infected cells release

100,000 virions

experts estimate that _____ of cancers are caused by

13% of cancers are caused by viruses

human cell has around _______ genes

21,000 genes

poxvirus infected cells release

3000 to 4000 virions

how many genes in hepatitis B virus

4 genes

how many genes does Escherichia coli contain

4,000 genes

international committee on the taxonomy of viruses

8 orders and 38 families (another 84 families not yet assigned to any order)

How much of the human genome consists of viral sequences 0.8% 1% 5% 7% 8% 10% 15% 20%

8%

____% of the human genome consists of

8% sequences that come from viruses

how many genes in HIV human immunodeficiency virus

9 genes

Classical Creutzfeldt-Jacob disease is ________. A. caused by a chronic latent virus B. initiated by an oncogenic virus C. caused by a viroid D. a spongiform encephalopathy of humans E. also called "mad cow disease"

D. a spongiform encephalopathy of humans

Infectious naked strands of RNA that affect plants are called A. spikes B. prions C. satellite viruses D. viroids E. phages

D. viroids

what two people showed that a disease in tobacco was caused by a virus

Dimitri Ivanoski and Martinus Beijerinck

what do T Even Bacteriophages infect

Escherichia coli

Viroids size

about one-tenth the size of an average virus

inside of a host cell, viruses are

active

Viruses are better described as __ or ___ rather than _______ or ______

active or inactive rather than alive or dead

temperate phage undergoes

adsorption and penetration, but do not undergo replication or release immediately

Variant CJD has strong evidence that

agent responsible for VCJD in humans is responsible for BSE in cows

viruses infect

all types of cells, including bacteria, algae, fungi, protozoa, plants, and animals

Loeffler and Frosch discovered

an animal virus that causes foot and mouth disease in cattle

Chronic Wasting Disease is fetal to

animals and there are no treatments or vaccines

because viruses exhibit specific host specificity, some

animals can allow a virus to grow more readily than others

how could Bovine Spongiform Encephalopathy possibly originated

as a result of feeding cattle meat and bone meal that contained Bovine Spongiform Encephalopathy infected products from a spontaneously occurring cause of BSE or scrapie infected sheep products

oncogenic

cancer causing viruses

6. release

enveloped viruses bud off of the membrane, carrying away an envelope with the spikes. this complete virus or virion is ready to infect another cell

Kuru

epidemic occurrence in the 1950-60s among the Fore people of New Guinea

estimated _____ virus particles on

estimated 10^31 virus particles on earth, which approximately 10 times the number of bacteria and archaea combined

regressive hypothesis

existing viruses may have evolved from more complex organisms that lost genetic information over time

Chronic Wasting disease does not appear to

naturally infect cattle or other domesticated animals

Bovine Spongiform encephalopathy is a

neurodegenerative disorder that rapidly progresses

Creutzfeldt-Jacob disease

neurodegenerative disorder that rapidly progresses

prions are _________ infectious agents

noncellular

budding of the enveloped viruses causes

them to be shed gradually without the sudden destruction of the cell

(lysogenic cycle) temperate phages: viral DNA enters an inactive prophase state, which is

then inserted into the bacterial chromosome and copied during the normal bacterial cell division

the structure of viruses only contains

those parts needed to invade and control a host cell

a virus can invade its host cell only

through making an exact fit with a specific host molecule

Synthesis: retroviruses

turn their RNA genome into DNA

viruses are (located)

ubiquitous in nature and have had major impact on development of biological life

viruses are ______________ in size, ranging from

ultramicroscopic in size, ranging from 20 nm up to 1000 nm in diameter

4. synthesis (replication and protein production)

under the control of viral genes, the cell synthesizes basic components of new viruses such as RNA molecule, capsomere, and spikes

archaeal viruses are

unique and not very understood

for many years, the cause of viral infections was

unknown

the length of the replication cycle

varies from 8 hours in polioviruses to 36 hours in herpesviruses

rabies infects

various cells of mammals

every bacterial species is parasitized by

various specific bacteriophages

General phases of the animal viral replication cycle EXCEPT: Adhesion Penetration Uncoating Synthesis Assembly Release

Adhesion (its adsorption)

provirus

viral DNA incorporated into the DNA of the host

Hepatitis D requires

viral particles from Hepatitis B to replicate

segmented RNA

individual genes exist on separate pieces of RNA (similar to human chromosomes)

prions are class of

infectious diseases called transmissible spongiform encephalopathies (TSEs)

This image shows what type of capsid -complex -naked -enveloped

naked

enveloped viruses can bud from

-cell membrane -nuclear envelope -endoplasmic reticulum

viruses lack

-enzymes for most metabolic processes -machinery for synthesizing proteins

Spikes can be found on ________ or ______ viruses

naked or enveloped viruses

filterable virus

-these early researchers found that when fluid from host organisms passed through porcelain filters designed to trap bacteria, the filtrate remained infectious -this proved that infection could be caused by fluid containing agents smaller than bacteria

Human prions diseases

1. Creutzfeldt-Jakob disease (CJD) 2. Variant Creutzfeldt Jakob Disease 3. Gerstmann Straussler scheinker syndrome 4. Fatal Familial Insomnia 5. Kuru

general phases of the animal viral replication cycle

1. absorption 2. penetration 3. uncoating 4. synthesis 5. assembly 6. release

events of lytic cycle of bacteriophages

1. adsorption 2. penetration 3. synthesis (duplication of phage components) 4. assembly of new virions 5. maturation 6. lyse of weakened cell

animal prion disease

1. bovine spongiform encephalopathy 2. chronic wasting disease 3. scrapie 4. transmissible mink encephalopathy 5. feline spongiform encephalopathy 6. exotic ungulate spongiform encephalopathy

virus structure contains

1. external coating (capsid) 2. core containing nucleic acid (DNA or RNA) 3. matrix proteins or enzymes (occasionally)

cell culture or tissue culture

1. grown in sterile chambers with special media that contain the nutrients for the cell to survive 2. cells for a monolayer or single confluent sheet of cells that supports viral multiplication 3. allows for the close inspection of culture for signs of infection

capsid (capsomere) two primary types

1. helical 2. icosahedral

the newer system of virus classification emphasize on (4 things)

1. host and diseases they cause 2. structure 3. chemical composition 4. similarities in genetic makeup

transformed cells

1. increased rate of growth 2. changes in their chromosome 3. changes in the cell's surface molecules 4. capacity to divide indefinitely

why are bird egg containing embryos used

1. intact self-supporting units 2. sterile environment 3. contain their own nourishment

primary purpose of viral cultivation

1. isolate and identify viruses in clinical specimens 2. prepare viruses for vaccines 3. do detailed research on viral structure, multiplication cycles, genetics, and effects on host cell

inherited forms of CJD include

Gerstmann Straussler Scheinker Syndrome Fatal Familial Insomnia

example of satellite viruses

Hepatitis D (delta virus)

Which is NOT a potential origin method of viruses Progressive Hypothesis Reductive Evolution Regressive Hypothesis Pre-life Hypothesis Virus First Escaped Gene Hypothesis All of these are correct

Pre-life hypothesis

early earth only contained

RNA

nucleic acid can be either

RNA or DNA, but not both

Which of the following is FALSE about viruses -They contain either RNA or DNA -They cannot infect algae -An example of a giant virus is mimivirus -Virus is latin for poison -Early researchers utilized a filtration experiment in which the filtered fluid remained infectious

They cannot infect algae

enveloped viruses take

a bit of cell membrane when they are released from the host cell

Dimitri Ivanoski and Martinus Beijerinck showed that

a disease in tobacco (plant virus) was caused by a virus

a carrier relationship between the cell and virus can last

a few weeks to the remainder of the host's life

regressive hypothesis: viruses adopted

a parasitic approach to replication

viroids are composed of

naked strands of RNA, lacking a capsid or any other coating

Viruses with a complex capsid infect what type of organism

bacteria

obligate intracellular parasites are found in

bacteria, protozoa, fungi, algae, plants, and animals

viruses that can infect bacteria are called

bacteriophages

examples of archaeal viruses

bottle shaped viruses spindle shaped viruses two tailed viruses whose tails "grow" once they are released from the infected cell

Clostridum botulinum acquire

botulinum toxin

satellite nucleic acid

cannot encode their own capsid protein

obligate intracellular parasites

cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to make and release new viruses

what is the most prominent feature of viruses

capsid

what is always found in viruses

capsid and core nucleic acid

some cells maintain a __________ relationship, which means

carrier relationship, means the cell harbors the virus and is not immediately lysed

retroviruses

carry their own enzymes to convert RNA to DNA

what organism does Bovine Spongiform Encephalopathy affect

cattle

viruses bear no resembles to

cell and lack any of the protein synthesizing machinery found in cells

in vitro

cell or tissue culture methods

viruses infect

cells and influence their genetic material

having a larger genome allows

cells to carry out complex metabolic activity necessary for independent life

most common bird embryos used are

chicken duck turkey eggs

Vibrio cholera acquire

cholera toxin

vCJD has different

clinical and pathological characteristics from classic CJD

cell culture/ tissue culture: allows for the

close inspection of culture for signs of infection

3. uncoating

conditions within the endosome cause fusion of the vesicle membrane with the viral envelope, followed by release of the viral capsid and RNA into the cytoplasm

naked viruses

contain no outer layer just the capsid and nucleic acid core

direct fusion of the viral envelope with the host cell membrane

envelope merges directly with the cell membrane, liberating the nucleocapsid into the cell's interior

chronic wasting disease affects

deer, elk, reindeer, sika deer, and moose

Corynebacterium diphtheriae acquire

diphtheria toxin

spikes allow viruses to

dock (attach) with host cells

most bacteriophages contain

double stranded DNA, but some RNA types exist as well

RNA viruses can be

double stranded, but more often single stranded

nucleic acid can be __________ or ___________ stranded

double to single stranded

minority of patients develop CJD

due to inherited mutations in the prion protein gene

complex capsid are never

enveloped

virus is a genetic element that contains

either DNA or RNA surrounded by a protein capsid and that replicate only inside the cell

satellite viruses

encode their own capsid proteins

penetration by

endocytosis happens when an entire virus is engulfed by a cell and enclosed by a vesicle or vacuole

Synthesis: DNA viruses

enter the host cell's nucleus and are replicated and assembled there

Hepatitis D has the highest

fatality rate among all the hepatitis infections, at 20%

outside of the host, viruses lack most

features of life making them inactive or inert

enveloped viruses are more

flexible than capsid, which means they are more pleomorphic

old system for classification of viruses

for many years, animal viruses were classified on the basis of their host and the diseases they caused

spikes are projected

from the nucleocapsid or the envelope

some viruses carry

genes that directly cause cancer

virus

genetic element that can multiple only in a living (host) cell

escaped cell steps (progressive hypothesis)

genetic fragments escaped from cell developed protective coating reentered the cell to hijack machinery to reproduce

mobile genetic element

genetic material capable to moving within a genome

vCJD and CJD have unique

genetic profile of the prion protein gene

Hepatitis D is found

globally, but predominantly in Africa, Middle East, and Southern Italy

cases of Bovine Spongiform Encephalopathy in the UK

have dropped sharply (less than 14,000 in 1995 and 2 in 2015)

`viruses do show some traits of life, such as

hereditary, development, and evolution, but do not show these characteristics independent of their living host

examples of chronic latent state

herpes simplex (cold sores and genital herpes) and herpes zoster virus) and herpes zoster viruses (chicken pox and shingles)

molecules (spikes) on virus surfaces give them

high specificity for attachment to host cells

high specificity

highly specific for what the virus can infect

viruses need

host cells for energy, metabolic intermediates, and protein synthesis

there are no reported ______cases of chronic wasting disease

human, but it may pose a risk to nonhuman primates

how many genes in herpesvirus

hundreds of genes

viruses are constructed from

identical protein subunits called capsomere

capsomere

identical protein subunits that make up the capsid

Variant Creutzfeldt Jakob Disease first described

in 1996 in the United Kingdom

viroids are a significant pathogen

in economically important plants, such as tomatoes, potatoes, cucumbers, citrus trees

complex capsid only found

in viruses that infect bacteria

isolated animal cells are grown

in vitro in cell or tissue culture rather than in an animal or egg

lysogeny a condition

in which host chromosome carries bacteriophage DNA

outside of a host cell, viruses are

inactive

poliovirus infects

intestinal and nerve cells of primates

ocassional laboratory animals include

invertebrates (insects) and nonhuman primates

one of the main reasons viruses are generally considered nonliving

is that they are not cellular

until the discovery of prions

it was considered impossible that an agent lacking genetic material could be infectious and transmissible

spikes act like _____ and allow for ______

keys and allow for specificity

in vivo

laboratory bred animals and embryonic bird tissue

carrier relationships can remain

latent in the cytoplasm

Bovine Spongiform Encephalopathy has led to

laws in developing countries to ban the use of rendered ruminants proteins in ruminants feed as a precaution against the spread of prion infections in cattle and other ruminants

DNA viruses that are double stranded can be

linear or circular

Hepatitis B virus infects

liver cells of humans

viruses require

living cells as their medium

the silent virus infection

lysogeny

plaques manifest as

macroscopic, round, clear spaces that corresponds to areas of dead cells

oncoviruses

mammalian viruses capable of initiating tumors

what is occasionally found in the structure of virus

matrix proteins and enzymes

examples of provirus

measles and HIV

prions are

misfolded proteins, which transmit their misfolded shape onto variants of the same proteins

progressive hypothesis

mobile genetic elements (genetic material capable of moving within a genome) gain ability to exit one cell and enter another cell

cell culture/ tissue culture: cells form a

monolayer or single confluent sheet of cells that supports viral multiplication

T Even Bacteriophages

most widely studied phages mainly because they infect Escherichia Coli

complex capsid have

multiple types of proteins and take shapes that are not symmetrical

negative sense RNA

must be converted before translation can occur

nucleocapsid

nucleic acid + protein in enveloped viruses

viruses have their own

nucleic acid genome

detection of viral growth in culture

observation of degeneration and lysis of infected cells

when was the first infection of Bovine Spongiform Encephalopathy

occurred in the 1970s and was identified in 1986

satellites are grouped

on common characteristics

satellites depend

on other viruses for replication

cancer causing viruses

oncogenic

what is the smallest virus

parvoviruses which is 20 nm in diameter

the flexible cell membrane of the host is

penetrated by the whole virus or nucleic acid

chronic latent state

periodically becomes activated under the influence of various stimuli

some animal viruses enter their host cell and

permanently alter its genetic material and many times can cause cancer

satellites have no common

phylogeny and are grouped on common characteristics

virus is latin for

poison

Kuru: government discouraged the

practice of cannibalism, which led to a continuing decline in the disease, which has now mostly disappeared

prions are composed

primarily of proteins and contain no nucleic acid

induction

prophage in a lysogenic cell becomes activated and progresses directly into viral replication and the lytic cycle

virus basic structure consists of

protein shell (capsid) surrounding the nucleic acid core

capsid

protein shell that surround the genome of virus

prions stand for

proteinaceous infectious particles

other viruses produce______ that induce

proteins that induce a loss of growth regulation, leading to cancer

Louis Pasteur hypothesized that

rabies was caused by a "living thing" smaller than bacteria

viruses have immense potential for

rapid viral proliferation

positive sense RNA

ready for immediate translation

regressive hypothesis also known as

reduction evolution

Synthesis: RNA viruses

replicated and assembled in the cytoplasm

What component are viruses missing -DNA -Double-stranded DNA -RNA -Ribosomes

ribosomes

viruses do not contain

ribosomes

Kuru was a result of

ritualistic cannibalism

capsomere spontaneously

self-assemble into the finished capsid

DNA viruses can be

single stranded (ss) double stranded (linear or circular)

virus architecture is best observed with

special stains and electron microscopy

In most patients (85%) of CJD occur

sporadically

cell culture/ tissue culture: grown in

sterile chambers with special media that contains nutrients for the cell to survive

prions exact mode of infection is

still being investigated

satellites are

subviral particles

During which phase of the animal viral replication cycle do we see nucleic acid replication and protein production Adsorption Penetration Uncoating Synthesis Assembly Release

synthesis

viruses multiply by

taking control of the host cell's genetic material and regulating synthesis and assembly of new viruses

lysogeny contains the

temperate phage

occasionally, phage genes in

the bacterial chromosome can cause the production of toxins or enzymes that the bacterium would not otherwise have

transformation

the effect of oncogenic viruses on the cell

most biologist now agree that

the first replicating molecules consisted of RNA, and not DNA

In 1884, Louis Pasteur developed

the first vaccine for rabies

viruses posses only

the genes needed to invade host cells and redirect their activity

virion

the infectious virus particle; the viral genome surrounded by a protein and sometimes a outer layer

Host range

the limited range of cells that a virus can infect

the number of viral genes in a virus is_________ ________ compared

the number of viral genes in virus is quite small compared to that of a cell

release

the number of viruses released by infected cells is variable, controlled by the size of the virus and health of host cell

Hepatitis D worsens

the severity of liver damage

lysogeny

the silent virus infection

genome

the sum total of genetic material carried by an organism

1. absorption

the virus attaches to its host cell by specific binding of its spikes to cell receptors

2. penetration

the virus is engulfed by the cell membrane into a vesicle or endosome and transported internally

virus have shaped

the way cells, tissues, bacteria, plants, and animals have evolved

5. assembly

viral spike proteins are inserted into the cell membrane for the viral envelope; nucleocapsid is formed from RNA and capsomeres

infectious virus particle

virion

assembly

virus is put together using parts manufactured during the synthesis process

Viroids

virus like agent that parasitizes plants

prions are not

viruses

what is the most abundant entity on earth

viruses

how are bird embryos used in virus testing

viruses are injected through the eggshell by drilling a small hole or making a small window

viruses are _____ _____ that seize control

viruses are minute parasites that seize control of synthetic and genetic machinery of cells

viruses are ____ cells and their structure

viruses are not cells and their structure is very compact and economical

viruses do not _______________ fulfill the

viruses do not independently fulfill the characteristics of life

enveloped viruses

viruses have an outer layer consisting of phospholipid bilayer (from host cell membrane) and viral proteins

virus first

viruses may have existed in a precellular world as self-replicating units, those units then became more organized and more complex

plaques develop when

viruses released by an infected host cell radiates out into adjacent host cells and new cells become infected, die and release more viruses

bacteriophages

viruses that can infect bacteria

lysogenic conversion

when a bacterium acquires a new trait from its temperate phage

usual choices for laboratory animals

white mice rats hamsters guinea pigs rabbits


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