VBS 2032: CH 13 LearnSmart

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

Transduction

Which of the following best describes viruses?

Infectious agents

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

Integrase

Which of the following about classifying viruses is FALSE?

It is not as important as classifying organisms since they are not living entities

When two different strains of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in _______

antigentic shift

Duration the _________ or maturation step in viral multiplication, capsids and genetic material are packaged into virions.

assembly

The image shows the ______ stage of the lytic cycle of the T4 phage.

assembly

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

Lysogenic conversion

Productive infection

New viral particles are produced

Reverse transcriptase is a(n) _____ polymerase

RNA-dependent DNA

Which of the following are viral protein components that attach to specific receptors on host cells?

Spikes and tail fibers

List the steps of an animal virus infection cycle in the correct order

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

Rank the following by size, from the smallest to largest, starting with the smallest at the top

1. Viruses 2. Bacteria 3. Human cells

Which of the two major categories of viral infections?

- Acute - Persistent

Replication of termperate phaves and lytic phages have which steps in common?

- Biosynthesis of viral components - Genome entry - Release - Attachment - Assembly

What are the two types of transduction?

- Generalized - Specialized

Viruses that infect bacteria are called

- Phages - Bacteriophages

Specialized transduction

- Results from errors in excision of the prophage - Transfers phage DNA and adjacent host genes - Produces defective phage particles

The study of viruses is important because

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

In a lysogenized bacterium, __________ of the prophage results in a lytic infection

excision

This image shows the _______ stage of the T4 phage lytic cycle

genome entry

The molecules that viral spikes attach to on the host cell in order to gain entry are typically:

glycoproteins

All of the following are required for synthesis of new virus particles in a host cell EXCEPT

homologous recombination

Lysogeny is best described as

intergration of the viral genome into the host chromosome

(-) strand genome

is the complement to mRNA

Some pathogenic bacteria produce toxins that are encoded on prophage DNA, and these are examples of ______ conversion

lysogenic

In enveloped viruses, sandwiched between the nucleocapsid and the envelope is the

matrix protein

One of the early proteins expressed in the T4 lytic cycle is an enzyme called a _________ that degrades the bacterial DNA

nuclease

Most animal DNA viruses will replicate within the host cell's

nucleus

Apoptosis

programmed cell death, a process some non-enveloped viruses trigger as a means of release

The virally encoded polymerase needed for replication of RNA viruses is called a

replicase

HIV is described as a ________ because it uses reverse transcriptase to make a DNA copy from its RNA genome

retrovirus

An enzyme that uses an RNA molecule as a template to make a complementary copy of DNA is called

reverse transcriptase

(+) strand genome

serves as mRNA

Viral proteins that stick out from the viral envelop or capsid and attach to host cell receptors are termed

spikes

Phage DNA and proteins are made during the _____ stage of T4 lytic cycle

synthesis

Phage heads that contain only bacteria DNA are called generalized _________ particles

transducing

After a virus enters a cell, the nucleic acid separates from the protein coat, a process called

uncoating

lysis

used to describe the rupture or bursting of a cell

Regarding animal viruses, which of the following statements are true?

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

Which of the following are diseases caused by prions?

- Bovine spongiform encephalopathy - Scrapie - Creutzfeldt-Jakob disease

Identify all the methods by which an enveloped virus can gain entry into animal cells

- Fusion of the viral envelope and the cell membrane - Endocytosis of the virus by the host cell

Which of the following occur during the synthesis stage of the T4 lytic cycle?

- Synthesis of phage DNA - Degradation of bacterial DNA - Synthesis of phage proteins

The hepatitis B virus sometimes causes an infection that results in a continuous and low-level production of virus particles. This type of infection pattern is specifically described as a(n) _________ viral infection

chronic

Infection of bacteria by ______ phages always end with the lysis of the host cell

lytic

Virus infections that result in the formation of new virus particles are described as

productive

Consequences of lysogeny include

- Immunity to superinfection - Lysogenic conversion

Which of the following are classified as persistent infection?

- Latent infections - Chronic infections

A viral infection in which the viral genome is integrated into an animal host cell chromosomes, yet can reactive to cause a productive infections, is categorized as a(n) _______ infection

latent

proofreading

RNA viruses have a higher mutation rate than DNA viruses because replicase lacks ______ ability

Replicases are _______ polymerases

RNA-dependent RNA

______ transduction is the result of excision error made as temperate phages transition from a lysogenic to a lytic cycle

Specialized

The accumulation of mutations in genes that encode viral surface proteins recognized by the immune system results in a type of antigenic variation called

Antigenic drift

Which of the following describes the various viral parts coming together to produce virions?

Assembly

This image shows the ______ stage of the T4 phage lytic cycle.

Attachment

Which types of viruses are released by budding?

Enveloped viruses

Which form of transduction results from excision errors during the transition from a lysogenic to lytic cycle?

Specialized

False

T or F: Enveloped viruses enter the host cell by endocytosis only, while non-enveloped viruses can enter host cell by fusion or endocytosis

False

T or F: Lysogens are more susceptible to reinfection by the same type of phage

False

T or F: Most bacteria engulf bacteriophages as part of the phage replication strategy

True

T or F: Viruses can contained either DNA or RNA, but not both

release

The stage of viral multiplication at which budding occurs is _____.

Latent state

Viral genome remains silent within the cell

Which is most important for attachment of a virus to a host cell?

Viral specificity for host receptors

A single virus particle is referred to as a

Virion

Which of the following statements about virus nucleic acid is true?

Viruses contain either DNA or RNA

Temperate; lytic

_____ phages have the option of entering the prophage state, while _____ phage always burst the host cell shortly after infection

A prion is best described as

a proteinaceous infectious agent

Infections that have a sudden onset of symptoms of relatively short duration are described as _______ infections

acute

The number of phage particles released from a host cell is called the _____ size

burst

A _____ is an infectious agent that lacks a capsid and consists only of RNA

viroid

Viruses are challenging to study because

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

Specialized transduction

- Transfers phage DNA and adjacent host genes - Results from errors in excision of the prophage - Produces defective phage particles

Which of the following processes are required for production of virus particles in a host cell?

- Translation of viral genes - Replication of viral genome - Transcription of viral genes

Which of the following are non-cellular infectious agents?

- Viroids - Prions - Viruses

Double-stranded genome

Consists of both a (+) and (-) strand

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 _______.

shift

Many animals viruses have proteins called ________ that attach to receptors on host cells

spike

Late proteins of the T4 lytic cycle include

- T4 tail fibers - T4 capsomere components

Which facts best support the position that viruses are not living organisms?

- Viruses are inert outside of a host - Viruses cannot reproduce on their own

Which of the following statements about viruses are true?

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

Which statements regarding viruses are true?

- Viruses that infect bacteria can be called phages - Viruses that infect bacteria can be called bacteriophages

Enveloped viruses can derive their envelopes from

- certain host organelles - the host cytoplasmic membrane

In order to infect an animal cell, viruses must

attach to receptors on the host cytoplasmic membrane

The binding of a bacteriophage surface protein to a host cell receptors is called

attachment

How does bacteriophage nucleic acid enter the host cell?

injection

Which of the following are non-cellular infectious agent?

- Viruses - Viroids - Prions

A ______ phage can either cause a lytic infection or can incorporate its DNA into the host genome as a prophage

Temperate

________ is a change in the phenotype of a lysogen as a consequence of the specific prophage it carries

lysogenic conversion