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