Micro Ch 6 Connect

What is larger than a typical bacterial cell?

A typical eukaryotic cell

Which is smaller, a typical protein or a typical virus?

A typical protein.

What is smaller, a typical bacterial cell or a typical virus?

A typical virus.

Which of the following best defines a temperate phage?

A virus that can integrate its genome into the host genome.

Many RNA viruses must _____ to replicate their genomes.

Carry their own enzymes

What are the three methods used by viruses to gain entry into host cells?

Endocytosis of the virus into the cell, fusion of the viral envelope with host cell membrane, injection of viral nucleic acid into the cell.

Viral spike proteins on the influenza virus that facilitate viral attachment to red blood cells are called _____.

Hemagglutinin

If you were to add holin to a bacterial cell, what would you expect to happen?

Holes to form in the cell membrane

The energy for viral replication, gene expression, and nucleocapsid assembly comes from _______.

Host ATP

RNA viruses always encode the enzymes needed to replicate their genomes because _________.

Host cells typically do not have ways to make RNA from RNA templates.

An icosahedral capsid ________.

Is a regular polyhedron

A helical capsid _________.

Is shaped like a hollow tube with protein walls.

What things are larger than the average virus?

Mitochondrion, fungal cell, animal cell.

Regarding the efficiency of accommodating genes in the genome, viruses are considered ______ efficient than bacteria and eukaryotes.

More

DNA is incorporated into the T4 phage head by proteins called the ______.

Packasome

Protomers that combine as groups of five to make capsomers are called _________.

Pentons

Viruses that have a somewhat variable shape due to the viral envelope are called _______.

Pleomorphic

What is different between a naked and not naked virus?

Presence of an envelope

Kuru, Creutzfeldt-Jakob disease, fatal familial insomnia, and Gerstmann-Strassler-Scheinker syndrome are human disease caused by ____.

Prions

Select the two main advantages that explain why lysogeny evolved in bacteriophages.

Viral nucleic acid can be maintained in a dormant host, the bacteriophage can survive at a high multiplicity of infection.

For viruses that enter an animal cell by endocytosis, the endocytic vesicle fuses with an endosome. What is NOT TRUE regarding viral uncoating?

Viral uncoating is always complete before the nucleic acid is released to the cytosol. The high pH of the endosome often triggers viral uncoating.

35. Spikes, or peplomers, are _____.

Virally-encoded proteins that project from the envelope surface

Bacteriophages that always proceed to lyse the infected cell are called _____ phage.

Virulent

An acellular infectious agent that must replicate within a host cell is a(n) ___________.

Virus

In the context of virus replication, fusion with the host cell membrane, injection of nucleic acid, and endocytosis are the three modes of _________.

Virus entry into host cells

Viral genes are classified as early, middle, or late based on ________.

When they are expressed during the infection

Most bacterial and archaeal viruses have ____ genomes.

dsDNA

A single virus could have which genomes _____.

dsDNA, dsRNA, ssDNA, or ssRNA

What are the steps in RNA silencing?

dsRNA is cut into small fragments, viroids hybridize to specific host mRNA molecules, Normal host cell functions are compromised.

The RNA of viroids encodes how many gene products?

0

Arrange the steps in Delbruck and Ellis' one-step growth experiment in chronological order, with the earliest step at the top.

1.Mix T4 phage with E. coli bacteria 2.Wait a short period to allow viral attachment 3.Dilute the culture so virions don't infect new cells, then incubate 4.Remove samples over time to determine the number of infectious phage particles

The size of a viral genome can be _______.

4,000 to 2,500,000 nucleotides long

Lysogenic conversion occurs when ________.

A phage gives new phenotypic properties to a bacterial cell.

What is most likely to function as a viral receptor on a host cell surface?

A protein important in normal cell function that is always present.

Middle proteins in a viral life cycle function to _____.

Activate expression of late genes, replicate the viral genome.

Neuraminidase is an enzyme found in the spikes of influenza virus that ______.

Allows mature virions to leave infected cells.

What best describes a virus?

An acellular infectious agent that can only replicate within a host cell.

Give the correct order for a typical viral life cycle beginning with the virus "floating around" in the environment.

Attachment, entry, synthesis, self-assembly, release

Viruses that infect bacterial cells are called ____________.

Bacteriophages

=Examples of viral ligands on bacterial and archaeal viruses include ________.

Beard-like fiber clusters, tail fibers, claw-like structures.

If a tumor cell remains in place to form a compact mass, the tumor is said to be _____.

Benign

What types of viruses can use endocytosis as a means of viral entry?

Both enveloped and naked viruses.

Viruses exist ______ cells.

Both outside and inside

All known prion diseases cause degeneration of what tissue?

Brain

The protein coat that surrounds the viral nucleic acid is called the ______.

Capsid

Either five or six protomers usually combine to make each ________ in icosahedral viral capsids.

Capsomer

Icosahedral capsids are composed of repeating ring- or knob-shaped protein subunits called _______.

Capsomers

Plant viruses require ______ to infect the cell.

Cell wall damage

Examples of viral receptors on bacterial cells include

Cell wall polysaccharides, teichoic acids, flagella

The best definition of cytopathic effects caused by a viral infection of eukaryotic cells is _______.

Changes or abnormalities in infected cells that are distinct from lysis.

Which two eukaryotic cell endocytic pathways are used by some virions to enter the cell?

Clathrin-dependent endocytosis, macropinocytosis.

What are two components not found in viruses?

Cytoplasm and ribosomes.

What type of genome would seem simplest to replicate in a host cell?

DNA

Because viroids code for no enzymes of their own, it is believed that they are replicated by a normal host cell enzyme called ______.

DNA-dependent RNA polymerase

Fusion of an endocytic vesicle containing an enveloped virus with an endosome will promote uncoating because of ______.

Degradative enzymes in the endosome, the low pH in the endosome.

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

Detection and degradation of dsRNA

Most viruses can only be seen using a(n) _________.

Electron microscope

The specific process of an enveloped virus leaving the cell is called _______.

Endocytosis

20. Viruses with a lipid membrane are often called _________.

Enveloped

True or false: The cell membranes is the only host cell structure from which enveloped viruses obtain their envelope.

False

Late proteins in a viral life cycle function to ______.

Form the capsid, lyse the host cell

The term ______ refers to the merging of the viral envelope and a host cell membrane.

Fusion

Protomers that combine as groups of six to make capsomers are called _____.

Hexons

Budding is best described as ______.

How enveloped viruses acquire their membranes

During T4 bacteriophage release, lysozyme will ______.

Hydrolyze the peptidoglycan cell wall

What name is given to the process that leads a lysogenic virus to transition to the lytic cycle?

Induction

When a change in conditions causes a prophage to begin synthesizing and assembling new virions, this is called _______.

Induction

Because they can inhibit infection of the same cell by more than one virion, temperate bacteriophages have an advantage at a high MOI, which stands for multiplicity of _______.

Infection

What is the prion protein known as PrPSC?

It is the abnormal form of PRPC, which is a normal cellular protein. PrPSC accumulates in the brain of animals with scrapie.

Arrange the parts of a viral growth curve determined by the one-step growth experiment performed by Delbruck and Ellis.

Latent period, rise period, plateau

Virus will attach to host cells via a viral ______ and a host receptor.

Ligand

A viral envelope is composed of primarily ______.

Lipids

Most viruses will leave a host cell by bursting the cell, a process called _________, or by pushing through the cell membrane while taking some of that membrane with it, a process called ________.

Lysis, budding

Bacteria infected by temperate phages are called _____ bacteria

Lysogenic

_____ ______ is when a temperate phage causes a change to the phenotype of an infected bacterial cell.

Lysogenic conversion

When a temperate phage integrates its genome into a host genome, the relationship between the phage and the host is termed ______.

Lysogeny or lysogenic cycle.

What is the protein that facilitates the nucleocapsid docking with a lipid raft of viral proteins in influenza virus budding from the host cell?

Matrix (M) protein

Cells from cancerous tumors actively spread throughout the body in a process known as ______.

Metastasis

Which of the following describes the role of tumor suppressor proteins?

Most regulate cell division

Viruses that lack a viral envelope are often called _________.

Naked

A tumor is a growth or lump of tissue resulting from _____, which means unregulated abnormal new cell growth and reproduction of a similar cell type.

Neoplasia

Do viruses contain ATP or a lipid bilayer?

No

What effect would lysozyme have on a eukaryotic cell?

None

What are the four cellular structures that can be the source of viral envelopes?

Nuclear membrane, plasma membrane, golgi apparatus, endoplasmic reticulum.

The simplest viruses consist of nucleic acid surrounded by a protein coat. This composite structure of viral nucleic acid and protein is called a ________.

Nucleocapsid

The main difference between virulent phage and temperate phage is that virulent phage _____.

Only have a lytic cycle.

The virus-associated pyramids found in Sulfolobus cells infected with STIV function to release virions by ______.

Opening like flower petals.

Viroids cause disease in what type of host?

Plants

A host cell that contains a _______, the nucleic acid of a temperate phage, can divide many times.

Prophage

The nucleic acid of a temperate phage that is either integrated into the host cell's genome, or remains free in the cytoplasm, is called a ________.

Prophage

The main difference between proto-oncogenes and tumor suppressor genes is that _______.

Proteins encoded by proto-oncogenes normally stimulate cell division; proteins encoded by tumor suppressor genes normally inhibit cell division.

Capsids are generally composed of repeating proteins subunits called ________.

Protomers

During T4 bacteriophage release, holin will ______.

Put holes in the cell membrane.

Viroids are infectious agents that consist of ______.

RNA only

Because their host cells typically lack the appropriate enzymes, which type of viruses always encode the enzymes needed to copy their genome?

RNA viruses

Which two of the following are tumor suppressor proteins?

Rb, p53

Which of the following virus "life" cycle steps is used to describe the lysis of the host cells?

Release

Once a virus enters the cytoplasm of a host cell, it begins to _____.

Replicate its genome

What are examples of lysogenic conversion?

Salmonella producing novel lipopolysaccharides, Corynebacterium diptheria causing diptheria.

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

Satellite

Identify the major difference between satellite viruses and satellite nucleic acids.

Satellite viruses are composed of nucleic acid and protein. Satellite nucleic acids are composed of DNA or RNA only.

Viral genomes composed of multiple pieces of RNA are called _____ genomes.

Segmented

he viral encoded proteins that project from a viral envelope surface are called _______.

Spike proteins

Which viral life cycle step generally occurs after the virus has uncoated?

Synthesis

Early proteins in a viral life cycle function to _______.

Take over the host cell

Bacteriophages that can integrate their genome into the host genome are called ______.

Temperate or lysogenic

Enveloped viruses gain their envelope from ______.

The host cell membrane

The length of the capsid of a helical virus like TMV is determined by ________.

The length of viral nucleic acids to be enclosed

What is NOT true regarding the packaging of DNA into the T4 phage head are false?

The packasome proteins catalyze the fusion of the head and tail assembly. DNA is incorporated into the head by a complex of proteins called the viroplasm.

The diameter of the capsid of a helical virus like TMV is determined by _______.

The size and shape of the protomers.

What best describes viral tropism?

The specific cell type that a virus can infect

What are the characteristics of prion diseases in humans and other animals?

There are no cures or effective treatments, they are uniformly fatal, they cause brain degeneration.

What can lysogenic viruses do?

They CAN reproduce normally, CAN become pathogenic, and DO copy viral RNA when they reproduce.

Mutations in genes that encoding enzymes for DNA repair can be carcinogenic mutations because ________.

They allow DNA damage to accumulate

True or false, most viruses that infect plants require another organism or random event to damage the cell wall of the plant cell to gain access to the cell membrane.

True

True or false: Viruses that have RNA genomes must carry enzymes in their virion to aid in replication once in a host cell.

True

Which two viral activities occurs during "viral entry?"

Uncoating, penetration

Viroplasms differ from viral replication complexes (VRCs) in that ______.

VCRs are membrane-bound but viroplasms are free in the cytoplasm.

What events occur during the entry of paramyxovirus to a host cell?

Viral envelope glycoproteins interact with host cell membrane proteins, viral and host cell membranes fuse, formation of proteinaceous fusion pore, nucleocapsid enters host cell cytoplasm, viral enzyme begins synthesizing viral mRNA.

Viral specificity for a host cell type is dependent on _________.

Viral ligand and host receptor

A complete virus particle is called a(n) __________.

Virion

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

Viroid

The study of viruses is termed ______.

Virology

Some viruses carry out viral replication and assembly in a distinct area of the cytoplasm not enclosed by membranes. These regions are called ______.

Viroplasms

Viruses must replicate within a host cell because ________.

Viruses lack replication enzymes and resources.

In contrast to viral genomic DNA, which may be dsDNA, ssDNA, dsRNA, or ssRNA, cellular genomes are always ______.

dsDNA

Most plant viruses have ____ genomes.

ssRNA