Exam 3 problems

The process in which a prophage is excised from the host genome and the lytic cycle is initiated is called 

induction

Shortly after infection, bacteriophage T4 expresses an early protein that binds host RNaseE and directs it to degrade host mRNAs. This is important for the viral life cycle because

it provides ribonucleotides for T4 transcription.

The relationship between a temperate phage and the host cell is called

lysogeny

Warts are benign tumors on the skin caused by

HPV

1\.     Herpesvirus genomes are quite large and typically encode about proteins.

70-200

Edward Jenner is well known for his discovery in 1796 of a vaccine against the disease 

smallpox

In the  cycle, a bacteriophage integrates its genome into the host's chromosome

lysogenic cycle

Nucleocytoplasmic Large DNA (NCLD) viruses are often termed megaviruses because

they are large enough to be visible by light microscopy

1\.     Less than 2 minutes after T4 DNA has been injected in a host cell, viral mRNA known as  mRNA is synthesized by the host cell's \n \n

early; RNA polymerase

True or false: The enzymes required for a single-stranded DNA virus to carry out its life cycle are the same enzymes used by the host cell, so that the virus does not need to synthesize its own DNA or RNA polymerases.

true

are benign epithelial tumors on the skin caused by human papillomaviruses.

warts

Order the parts of a typical herpes virus starting with the outside layer at the top.

spikes

envelope

tegument

nucleocapsid

Before bacteriophage ΦX174 genome can be replicated or transcribed, it must be converted to the double-stranded ________ form.

replicative form

\
* the ΦX174 ssDNA genome has the same base sequence as viral mRNA and is therefore plus-strand DNA. For either transcription or genome replication to occur, the phage DNA must be converted to a double-stranded replicative form (RF)

Smallpox was once one of the most dreaded diseases, in part because it had a fatality rate of ______.

20-50%

Which three of the following are characteristics of human parvovirus B19?

* enveloped
* ssDNA genome
* spiral shape
* noneveloped
* icosahedral shape
* ssRNA genome

* ssDNA genome
* nonenveloped
* icosahedral shape

Nucleocytoplasmic Large DNA (NCLD) viruses perform the steps of their life cycle in the _____ of the host cell.

\

cytoplasm

Why is RNA-dependent RNA polymerase (RdRp) essential for every virus with an RNA genome?

\
Host cells have no enzyme to synthesize RNA from an RNA template.

The difference between the life cycles of double-stranded DNA viruses and single-stranded DNA viruses is that _____.

a. the methylation patterns on the DNA strands allow them to be distinguished

b. synthesis of the second strand in ssDNA viruses must occur before replication and transcription

c. ssDNA viruses use the enzyme reverse transcriptase to generate a replicative form

\
synthesis of the second strand in ssDNA viruses must occur before replication and transcription

For most viruses with a segmented genome, each segment encodes _____.

\
a single protein

Warts are benign tumors on the skin caused by ______.

HPV

Which group of RNA viruses has genomes that can act as a mRNA to be translated immediately upon release into the host cytoplasm?

\
Plus-strand RNA viruses

The genome of bacteriophage ΦX174 is _______.

\
plus-strand DNA

* ΦX174 ssDNA genome has the same base sequence as viral mRNA and is therefore plus-strand DNA

Which of the following is a plus-strand RNA virus that invades plants through abrasions or wounds?

TMV

The genome of a parvovirus is usually _____.

negative-strand DNA

Which viral enzyme is used for replication of all RNA viral genomes except the retroviruses?

\
RNA-dependent RNA polymerase

What must all negative-strand RNA viruses bring into the host cell?

\
RNA-dependent RNA polymerase

The genome of a virus that is composed of more than one distinct RNA or DNA molecule is referred to as ______.

segmented

For plus-strand RNA viruses, the negative-strand RNA molecule is synthesized by _____.

viral RNA-dependent RNA polymerase

Which two of the following are characteristics of the tobacco mosaic virus?

Minus-strand RNA virus

Plus-strand RNA virus

Helical shape

Icosahedral shape

plus-strand RNA virus

helical shape

Select all genera of influenza viruses that cause significant human disease.

*Influenzavirus* C

*Influenzavirus* D

*Influenzavirus* A

*Influenzavirus* B

\
*Influenzavirus* A

*Influenzavirus* B

How many enzymes are encoded by the parvovirus genome?

0

During a measles infection, Koplik's spots, which present as red spots with a bluish-white speck in the center, are typically found ______.

\
in the mucosal lining of the mouth

The genomes of negative-strand RNA viruses **cannot** be directly   by ribosomes.

translated

The genomes of negative-strand RNA viruses **cannot** be directly  by ribosomes.

translated

Rabies viruses belong to the family ______.

Rhabdoviridae

For most viruses with a segmented genome, each segment encodes _____.

a single protein

The Ebola virus was first recognized near the Ebola River located in ______.

the Democratic Republic of the Congo in Africa

Which group of RNA viruses has genomes that can act as a mRNA to be translated immediately upon release into the host cytoplasm?

\
Plus-strand RNA viruses

Select the **three** correct matches regarding influenza viruses.

*Influenza C*: can cause disease in humans

*Influenza B*: can cause disease in humans

*Influenza A*: does not cause disease in humans

*Influenza C*: does not cause disease in humans

*Influenza B*: does not cause disease in humans

Reason: 

Influenza viruses are in the family *Orthomyxoviridae.*

*Influenza A*: can cause disease in humans

\
*Influenza C*: does not cause disease in humans

*Influenza A*: can cause disease in humans

*Influenza B*: can cause disease in humans

The retroviral RNA genome is _______.

positive strand RNA

Place the events of a typical measles infection into the correct order.

\

1. after exposure, incubation period of 10-14 days commences
2. prodromal period is characterized by nasal discharge, cough, fever, headache, and conjunctivitis
3. 3-5 days after prodromal period, red maculopapular rash develops
4. rash lasts 5-7 days, may present with Koplik’s spots in the oral cavity
5. recovery begins soon after the rash is reported

The rabies virion is ____.

\
enveloped and bullet-shaped

Which two of the following conditions must be met before the __genome of a retrovirus can serve as a template__ for the synthesis of mRNA and new positive-strand genome molecules?

\
Methylation of the genome

Export from the nucleus to the cytoplasm

Conversion from positive-strand RNA to dsDNA

Integration into host's DNA

Cap-snatching from host mRNA

Conversion from positive-strand RNA to dsDNA

Integration into host's DNA

Select all correct descriptions of Ebola viruses.

Five separate species

Family *Filoviridae*

Brick-shaped virions

Double stranded DNA genome

Five separate species

Family *Filoviridae*

What is the function of the ribonuclease H component of the reverse transcriptase enzyme of HIV?

Place the steps involved in making a double-stranded DNA copy of the HIV single-stranded RNA genome into the correct order.

reverse-transcriptase makes a single-strand DNA copy of the HIV RNA genome

HIV DNA is duplicated to form a double-stranded DNA copy of the original RNA genome

the HIV RNA genome is degraded by ribonuclease H

reverse-transcriptase makes a single-strand DNA copy of the HIV RNA genome

the HIV RNA genome is degraded by ribonuclease H

HIV DNA is duplicated to form a double-stranded DNA copy of the original RNA genome

For plus-strand RNA viruses, the negative-strand RNA molecule is synthesized by _____.

viral RNA-dependent RNA polymerase

Retroviruses have a genome that is composed of _______.

ssRNA

During a measles infection, Koplik's spots, which present as red spots with a bluish-white speck in the center, are typically found ______.

in the mucosal lining of the mouth

Which of the following are found in the complex that enters the nucleus after a cell is infected by HIV?

Multiple select question.

Several host molecules

HIV protease

Integrase

dsDNA produced by RT

One of the original RNA genomes

Several host molecules

dsDNA produced by RT

Integrase

Retroviruses convert their positive-strand RNA genome into dsDNA with _______.

reverse transcriptase

What is the function of the ribonuclease H component of the reverse transcriptase enzyme of HIV?

Degradation of the viral RNA genome

Which group of RNA viruses has genomes that can act as a mRNA to be translated immediately upon release into the host cytoplasm?

Plus-strand RNA viruses

An infectious agent composed of only RNA is called a(n) .

viroid

The retroviral RNA genome is _______.

positive-strand RNA

Which of the following best describes the normal mechanism of RNA silencing in eukaryotic cells?

Detection and degradation of dsRNA

The HIV enzyme   is critical to inserting the copied double-stranded DNA viral genome into the host cell genetic material.

integrase

Which two of the following conditions must be met before the __genome of a retrovirus can serve as a template__ for the synthesis of mRNA and new positive-strand genome molecules?

Methylation of the genome

Integration into host's DNA

Conversion from positive-strand RNA to dsDNA

Export from the nucleus to the cytoplasm

Cap-snatching from host mRNA

Integration into host's DNA

Conversion from positive-strand RNA to dsDNA

Which of the following may be composed of RNA or DNA, encode one or more proteins, and must have a "helper" virus to replicate?

satellites

Because it makes a DNA strand from an RNA template, another term for the reverse transcriptase of HIV is ______.

\

RNA-dependent DNA polymerase

Viroids are infectious agents that consist of _____.

RNA only

Infectious agents composed entirely of protein are called _____.

prions

Arrange the steps in RNA silencing by viroids according to the order in which they occur, with the earliest event at the top.

Normal host cell functions are compromised.

Hybrid dsRNA is cut into small fragments.

Viroids hybridize to specific host mRNA molecules

Viroids hybridize to specific host mRNA molecules

Hybrid dsRNA is cut into small fragments.

Normal host cell functions are compromised.

All known prion diseases cause degeneration of ____ tissue.

brain

A(n)   is a disease agent that can either have a RNA or DNA genome and must have a helper virus to facilitate replication.

satellite

The stable association of one organism with another is called  , regardless of how the association affects each participating organism.

symbiosis

Which of the following best describes the normal mechanism of RNA silencing in eukaryotic cells?

Detection and degradation of dsRNA

A microbe that lives inside a host is called an _____.

endosymbiont

Which three of the following statements about prion diseases in humans and other animals are correct?

Multiple select question.

There are no cures or effective treatments.

They cause brain degeneration.

They affect heart function.

Vaccines can prevent these diseases.

They are uniformly fatal.

There are no cures or effective treatments.

They cause brain degeneration.

They are uniformly fatal.

Identify the common characteristic of cooperation and mutualism.

Both are symbiotic relationships.

A symbiotic relationship in which each partner receives some benefit, and each partner is dependent on the other, is _____.

mutualism

Aphids and *Buchnera aphidicola* bacteria are obligate mutualistic symbionts. Therefore, if the bacterial partner is separated from the insect and placed in a culture medium, the expected result would be that the bacteria would ____.

\

die

Many marine invertebrates, for example, sponges, jellyfish, and corals, harbor endosymbiotic dinoflagellates called _____.

zooxanthellae

A microbe that lives on the surface of a host can be called an _____.

ectosymbiont

In the *Riftia* worm-endosymbiotic bacteria association, the bacteria are chemolithotrophic, using _____ as an electron donor and oxygen as a terminal electron acceptor.

sulfide

A symbiotic relationship in which each partner receives some benefit, but each partner can also live independently is called _____.

cooperation

In the microbial interaction described as mutualism, the larger organism is described as the host, while the microbe is described as the _____.

mutualist

Some aphids form an mutualistic relationship with certain strains of the bacterial species *Buchnera aphidicola*. If such aphids are treated with antibiotics, ______.

they lose their bacterial symbionts and die

Which three of these animals are ruminants?

Multiple select question.

Rodents

Cattle

Camels

Horses

Birds

Giraffes

cattle

camels

giraffes

Marine invertebrates like sponges, jellyfish, and corals often harbor zooxanthellae, which are endosymbiotic _____.

dinoflagellates

The *Xenorhabdus nematophila - Steinernema carpocapsae* cooperative symbiosis is remarkable because ______.

he bacteria facilitate the nematode's reproduction

How are commensalism and amensalism similar?

They are both unidirectional associations.

Ruminants are said to have an "eat now, digest later" strategy, because after feeding on grasses, they spend vast amounts of time chewing a small ball of partially digested grasses called their 

cud

Endosymbiotic bacteria living inside of *Riftia* worms use sulfide as an electron donor and _____ as a terminal electron acceptor.

oxygen

An unidirectional relationship where one organism releases a compound that has an adverse effect on another is called _____.

\

amensalism

In the *Xenorhabdus nematophila - Steinernema carpocapsae* cooperative symbiosis, the advantage to *Xenorhabdus* is that _____.

it gets a steady supply of nutrients