question

Viruses have some of the properties of living organisms. Which of the following is a characteristic of all organisms, but not of viruses?

answer

capable of metabolism, ability to reproduce, grow in response to their environment conditions, (presence of a plasma membrane)

question

Viruses are referred to as obligate parasites because

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they use the host cell's nucleotides and enzymes to reproduce

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Which of the following structures do viruses use to attach themselves to the host cell and help viruses enter the host cells?

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viral spikes

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Some viruses have a lipid bilayer, also known as the viral envelope. The viral envelope most likely comes from the following source:

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host cell plasma membrane

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The advantage of the viral envelope includes:

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helps viruses infect new cells by fusion of the envelope with the host's plasma membrane.

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A naked virus

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has no membranous envelope

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DNA viruses are grouped into families based on the following characteristics except:

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presence of an envelope, whether DNA is single stranded or double stranded, whether DNA is linear or circular, (presence of a capsid)

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The families of RNA viruses are distinguished from one another by all of the following except

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presence of an envelope, presence of a capsid and its shape, sense or nonsense RNA, (whether RNA is linear or circular)

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Viruses that have a single strand of RNA that acts as a template for DNA synthesis are known as

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retroviruses

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You have isolated an unknown virus. It is a double-stranded DNA and does not have an envelope. To which virus family does it mostly likely belong?

answer

adenoviridae

question

Common cold and flu are caused by which of the following pair of viruses?

answer

rhinovirus - orthomyxoviridae

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All of the following viruses may stay inside of a cell for many years and remain inactive except

answer

herpes, chickenpox, HIV, (enterovirus)

question

Acquired Immune Deficiency Syndrome (AIDS) is caused by a retrovirus. Which of the following best represents the genetic information flow used by retroviruses?

answer

RNA _ DNA _ mRNA _ protein

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The reason that retroviruses can direct the formation of DNA from RNA is because most retroviruses contain the following enzyme

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reverse transcriptase

question

A viral infection is ineffective by the treatment of anti-RNA drug. The most likely reason is that this virus is a

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poxvirus

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A latent viral infection is an infection in which

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a viral replication has stopped

question

Which of the following viruses are known for causing latent infections?

answer

herpesviruses

question

Which of the following is not caused by a poxvirus?

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smallpox, cowpox, monkeypox, (chickenpox)

question

Reactivation of chickenpox long after the initial infection leads to the disease

answer

shingles

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Viruses can be grouped into the following categories except:

answer

animal viruses, bacterial viruses, plant viruses, (fungal viruses)

question

A virus that is specific for a bacterial host is called

answer

phage

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Severe acute respiratory syndrome (SARS) is a viral respiratory illness that was first reported in Asia in 2003. Which of the following viruses was identified as the cause for SARS in humans?

answer

Coronaviruses

question

The virus that causes human severe acute respiratory syndrome (SARS) infects all of the following except

answer

humans, dogs and cats, birds, (snakes)

question

Why is there concern about the recent outbreak of avian influenza in Netherlands? Because

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human influenza may exchange genetic material with avian influenza and infect humans.

question

Which of the following is a FALSE statement about yellow fever?

answer

the first human disease found to be caused by a virus, the first confirmation that an insect could transmit a virus, caused by a flavivirus, its first name was yellow jack, (endemic to the United States)

question

Which of the following represents the correct order of steps in a typical virus replication cycle?

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adsorption _ penetration _ synthesis _ maturation

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Assembly of new viral components into a complete virion takes place during viral

answer

maturation

question

Which of the following is used by negative strand RNA viruses such as measles and influenza during their replication cycle?

answer

synthesize a double stranded RNA intermediate

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Much of the information about how viruses work has been gleaned from studying T seven phages that infect

answer

bacteria

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Bacteriophages contain the enzyme lysozyme, which is used to

answer

weaken bacterial cell walls

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31. Bacteriophage DNA is transcribed to mRNA during the ________ phase of viral replication.

answer

synthesis

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What would be a reasonable number of new phages to expect from one round of viral replication in one cell?

answer

100

question

Because viruses such as bacteriophages lead to bursting of the bacterial host cell they are known as________ viruses.

answer

lytic

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Plaques are

answer

areas where bacterial cells have been lysed

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Temperate phages

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do not always undergo a lytic cycle

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Viral DNA lying within a bacterial chromosome is called a ________ while the combination of a bacterial cell and its temperate phage is called a ________.

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prophage, lysogen

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Prophages are responsible for production of the toxins found in

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Clostridium botulinum

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Growth of a bacterium which contains a prophage represents a

answer

lysogenic cycle

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A lysogenous phage which enters a lytic cycle is said to have undergone

answer

induction

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Recognition of the proper host cell by an animal virus may be aided by the ________ of the virus.

answer

spikes

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All of the following reasons explain why eggs are often used to grow animal viruses except

answer

eggs are large cells, eggs are sterile, eggs contain a number sites that are suitable for viral replication, (eggs are easy to store)

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Cells taken directly from an animal and cultured in vitro represent

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primary cell cultures

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Enveloped animal viruses typically leave the host cell by

answer

budding

question

A drug or other agent that induces defects during embryonic development is known as a

answer

teratogen

question

A prion is made of which of the following?

answer

proteins

question

Diseases such as Creutzfeld-Jacob disease, kuru, and mad cow disease are caused by

answer

prions

question

Viroids are composed of

answer

single-stranded circular RNA

question

Which of the following viruses plays an important role in the development of cervical cancer?

answer

papilloma viruses

question

A rare form of cancer that has become common among men with AIDS is

answer

Kaposi's sarcoma

question

The most conclusive evidence that viruses cause cancers is provided by the following:

answer

development of a cancer following an injection of viruses

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Some liver cancer patients are found to have had chronic liver infection. The most likely cause of this infection is by

answer

hepadnaviruses

question

Which of the following explains how DNA tumor viruses may cause human cancers?

answer

viral proteins block the effect of tumor-suppressor genes which prevent uncontrolled cell division

question

The only RNA tumor virus that causes human cancer is

answer

retroviruses

question

Computer virus and biological virus are similar at

answer

Self-replicatio, dependence, Selectivity, infectiousness, (all the above)

question

Computer virus and biological virus are different at

answer

transfer media, damage level, host type, (All the above)

question

Key terms: virus

answer

an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.

question

Key terms: capsid

answer

A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres.

question

Key terms: enveloped

answer

The plasma membrane and cell wall complex of a bacterium.

question

Key terms: lysogeny

answer

is one of two methods of viral reproduction (the lytic cycle is the other). Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium's genome or formation of a circular replicon in the bacterium's cytoplasm.

question

Key terms: lytic cycle

answer

is one of the two cycles of viral reproduction, the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane.

question

Key terms: host range

answer

is usually a function of an inability of the virus to successfully adsorb and/or enter cells because of an incompatibility between virus capsid proteins (or virus envelope proteins ) and the host receptor molecule.

question

Key terms: restriction

answer

An enzyme that catalyzes the cleavage of DNA at restriction sites, producing small fragments used for gene splicing in recombinant DNA technology and for chromosome mapping

question

Key terms: dodder

answer

any of a genus (Cuscuta) of wiry twining vines of the morning-glory family that are highly deficient in chlorophyll, are parasitic on other plants, and have tiny scales instead of leaves

question

Key terms: prion

answer

have been held responsible for a number of degenerative brain diseases, including mad cow disease, Creutzfeldt-Jakob disease, fatal familial insomnia, kuru, and an unusual form of hereditary dementia known as Gertsmann-Straeussler-Scheinker disease.

question

Key terms: adenoviridae

answer

Adenoviruses are medium-sized, nonenveloped viruses with an icosahedral nucleocapsid containing a double stranded DNA genome. Their name derives from their initial isolation from human adenoids in 1953.

question

Key terms: orthomyxoviridae

answer

The Orthomyxoviruses are a family of RNA viruses that includes six genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus, Thogotovirus and Quaranjavirus.

question

Key terms: retrovirus

answer

Retroviridae is a family of enveloped viruses that replicate in a host cell through the process of reverse transcription.

Microbiology – 03 (Exam 1) – Flashcards

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