Microbiology Chapter 8

Plant viruses often gain entry into host cells by

injury caused by insects to host cell

Most likely, "host specificity" of a virus is determined by

the interactions between viral attachment proteins and host cell receptors

Class III viruses, double stranded RNA viruses, utilize the following polymerase for genome synthesis

viral RNA-dependnet RNA polymerase

Many antiviral drugs are nucleoside analogs. The nucleoside analogs primarily target these enzymes

viral nucleic acid polymerases

The influenza virus gains entry into a host cell by an endocytotic process. The viral nucleocapsid leaves the endoscope and enters the cytoplasm through a membrane fusion mechanism. Fusion of the viral envelope with the eadosomal membrane is facilitated by

a confirmation change in the hemagglutinin to expose a fusion protein

A bacteriophage genome that is integrated into the bacterial chromosome is called

a prophage

A chemical that is structurally similar to normal nucleoside is called a nucleoside

analog

Antibodies produced in response to a viral infection may specifically bind to the virus particle to effectively block ____ to the host cell

attachment

Antibody produced in response to a viral infection is able to neutralize viral attachment by

binding to the viral attachment proteins to prevent attachment to the host cell receptor

Most enveloped viruses exit the cell by the following process

budding

A viral fusion peptide contins a short hydrophobic amino acid sequence that helps facilitate membrane fusion of the viral envelope to the cell membrane for entry into the host cell. The protein ____ functions as a fusion peptide for HIV entry into the host cell.

gp41

Bacteriphage T4 lyses the bacterial host cell for realease of newly formed virions. The cell wall of the bacterium is broken down by this virally encoded enzyme

lysosome

Most non-enveloped viruses enter the host cell by receptor-mediated endocytosis. The virus or its nucleic acid is able to leave the endoscope and enter the cytoplasm

through pores formed viral capsid proteins

Fuzeon is an antiviral drug that prevents membrane fusion of entry into the cell by HIV. The mode of action for this drugs is

to bind gp41 membrane fusion protein of HIV

The reason nucleoside analogs are effective against viral nucleic acid polymerases is because

viral polymerases have a high affinity for incorporation of the analogs

The enzyme ____ has a high affinity for AZT and will incorporate it into newly synthesized DNA strand. This will effectively terminate DNA replication because the incoming nucleotide cannot be bound to AZT.

viral reverse transcriptase

Most enveloped viruses exit their host cell through a process called

budding

Most non-enveloped viruses exit the cell by the following process

cell lysis

Phage lambda (upside down Y) is referred to as a temperate phage. What is a temperate phage?

A phage that can undergo either a lytic or lysogenic phase of replication

Most enveloped viruses exit the host cell through cell lysis

False

The main function of a host cell receptor is to specifically bind to the viral attachment protein

False

Reverse transcriptase is an RNA dependent DNA polymerase

True

The second step in viral replication, "Entry" is prevented by some antiviral drugs

True

The single stranded RNA of positive sense RNA viruses can act directly as mRNA for translation in the cytoplasm of the host cell

True

Translation of mRNA for the production of viral proteins always takes place in the cytoplasm of eukaryotic cells

True

For most double-stranded DNA eukaryal viruses, DNA replication occurs in the _____ and translation occurs in the _____

nucleus, cytoplasm

Anitviral drugs that act at the level of host recognition are designed to

prevent virus binding to the host cell receptor

The intact vision of the tobacco mosaic virus is assembled by this method

the capsid proteins assemble around the viral nucleic acid

The ability of a virus or bacteriophage to specifically attach to a host cell occurs through the interactions of the viral attachment proteins with the host cell receport. This binding determines

the host range

AZT is a nucleotide analog used to treat people infected with

HIV

___ _____ ____

Receptor mediated endocytosis

Which of the following viral replication processes would not be a good target for an antiviral drug?

Translation of viral proteins

Class VII viruses, double-stranded DNA viruses that utilize reverse transcriptase, replicate their genome using the following polymerase

host cell DNA-dependent RNA polymerase

Class V viruses, negative sense single-stranded RNA viruses, utilize the following

viral RNA-dependent RNA polymerase

The viral attachment protein specifically binds to a host cell receptor. All of the following are examples of known host cell receptors except

DNA

A nucleoside analog is a short nucleotide sequence that is complementary to a viral promoter sequence

False

E. coli strain K12 is susceptible to infection by phage T2. T2 binds to K12 via two attachment proteins. These two proteins specifically bind tot he following two host cell receptor proteins found on the surface of strain K12

Ompf and lipopolysaccharide

Protease inhibits are routinely used in the treatment of an HIV infection to slow down the progression of the disease. How do these inhibitors work?

They inhibit the proteolytic modification of the viral capsid to form an infectious vision

Most RNA viruses utilize

an RNA-dependent RNA polymerase

A bacterial cell that contains the integrated genome of a temperate bacteriophage is called

lysogen

The second step in viral replication is entry. For bacteriophage, entry usually involves

direct entry of the nucleic acid into the cell

Class I viruses, double stranded DNA viruses, usually utilize the following polymerases for mRNA synthesis and DNA replication

host cell DNA-dependent RNA polymerase and host cell DNA-dependent DNA polymerase

The Baltimore classification scheme for viruses divides all viruses into seven groups based on

how they produce mRNA and replicate their genome

HIV enters the cell through a/an _____ mechanism

membrane fusion

Host _______ is determined through the specific binding of the viral attachment protein to the host cell receptor

range or specificity

Most non-enveloped animal viruses enter the host cell by

receptor mediated endocytosis

The influenza virus gains entry into a host cell by

receptor-mediated endocytosis

An HIV mutant has been identified that is resistant to the drug AZT. Most likely the mutation occurred in the viral gene that encodes for

reverse transcriptase

The Baltimore classification scheme classifies viruses based on their mechanism of mRNA synthesis. Using this classification scheme all viruses are placed into ____ classes

seven