MCRO 251 - Ch 13.1-13.2, 13.5-13.7

Late proteins of the T4 lytic cycle include ________.

T4 tail fibers T4 capsomere components

Some viruses trigger ________ as a means of being released.

apoptosis

In which phase of the T4 phage lytic cycle are new phage particles put together?

assembly

The binding of a bacteriophage surface protein to a host cell receptor is called ________.

attachment.

Animal viruses that don't have an envelope can only enter their host cell by ________.

endocytosis

The phospholipid bilayer found surrounding the capsid of some viruses is the ________.

envelope

M13 particles are assembled during a process called ________, which the virus uses to exit the cell.

extrusion

T/F: when a bacterial culture is infected with a temperate phage, all particles of the phage will lysogenize their host.

false

Which phage type causes productive infections that don't kill the host cell?

filamentous

ID all the ways 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

Replication of temperate phages and lytic phages have which steps in common?

genome entry biosynthesis of viral components release attachment assembly

Key characteristics used in the classification of viruses are ________.

genomic structure and host range

Temperate phages are more likely to enter the lysogenic cycle when bacterial cells are ________.

growing slowly

The M13 phage has a single-stranded DNA genome. Its replicative form is a double-stranded DNA molecule. The second strand of DNA is synthesized by ________.

host DNA polymerase

________ viruses have a capsid that is composed of twenty flat triangles.

icosahedral

Through the process of phage ________, a prophage is excised and enters the lytic cycle.

induction

What directs the incorporation of phage DNA into a bacterial chromosome?

integrase

The term ________ is used to describe the rupture or bursting of a cell.

lyse

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

lysogenic

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

lysogenic conversion

Consequences of lysogeny include ________.

lysogenic conversion immunity to superinfection

Match each possible outcome of phage replication with the correct definition

productive infection: new viral particles are produced latent state: viral genome remains silent within the cell

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

spikes

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

temperate

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

viral specificity for host receptors

Rank from smallest to largest human cells, viruses, bacteria

viruses, bacteria, human cells

List the steps of an animal virus infection cycle

1. attachment 2. penetration and uncoating 3. synthesis of viral proteins and replication of the genome 4. assembly 5. release

What suffix represents a viral family?

-viridae

What suffix represents a viral genus?

-virus -viridae represents a viral family

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

degradation of bacterial DNA, synthesis of phage DNA, synthesis of phage proteins

T/F: most bacteria engulf bacteriophages as part of the phage replication strategy

false

Because they are dependent on host cells, viruses are classified as ________.

obligate intracellular parasites

Lysogens are protected against infection by the same phage because the phage-encoded repressor protein binds to the ________ on the incoming phage, preventing expression of the phage genes.

operator

At a minimum, all viruses are composed of ________.

proteins (all viruses will have a capsid made of proteins surrounding nucleic acids) and nucleic aids (heritable material for replication)

Which of the following proteins is essential for maintenance of the lysogenic state?

repressor

A virus acquired by inhalation would be called a(n) ________.

respiratory virus

HIV is described as a ____ because it synthesizes DNA from RNA using reverse transcription

retrovirus

Infection of bacteria by ________ phages always ends with the lysis of the host cell.

virulent/lytic

Viruses that infect bacteria can be called ________ or ________.

bacteriophages, phages

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

burst

The study of viruses is important because ________, ________, ________.

there are many medically important viruses that cause disease; viruses can be a vehicle for horizontal gene transfer in bacteria; bacteriophages play a significant ecological role in reducing bacterial populations in nature

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

they are inert outside of a host, cannot reproduce on their own

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

transcription and translation of viral genes, replication of viral genome

T/F: bacteriophages are important medically because they can be used to prevent the growth of food-contaminating pathogens

true

T/F: viruses can contain either DNA or RNA, but not both

true