Microbiology Homework Chapter 26 Viruses

Rotavirus, the most common causative agent of diarrhea in infants and young children, is a member of the Reoviridae. Reoviridae is a(n) ________ in terms of virus nomenclature.

family

What is the HIV protein that is involved in attachment of the virus to host cells?

gp120

The type of cells infected by HIV are ________ early in the course of an infection and ________ late in the infection.

macrophages; helper T cells

Evaluate the statements below and choose those that are true regarding the differences between retroviruses and hepadnaviruses.

phone

Single-stranded RNA viruses containing a RNA genome that is identical to mRNA are called ________ RNA viruses.

positive-strand

Retroviruses have ________.

two copies of single-stranded RNA

Which of the following requires a reverse transcriptase to produce new nucleocapsids?

HIV

Which of the following utilizes reverse transcriptase to form DNA from a viral RNA template that is incorporated in the host DNA genome.

HIV

Which of the following requires an RNA-dependent RNA polymerase to produce new nucleocapsids?

Influenza virus

How do the genomes of HIV and influenza virus differ?

Influenza virus has a segmented genome comprising minus-stranded RNA, whereas the genetic material of HIV is not segmented and is plus-strand RNA.

The HIV enzyme that makes a double-stranded DNA copy of the viral genome is ________.

reverse transcriptase

The correct order of the stages for phage replication are 1 = assembly 2 = attachment 3 = transcription/replication 4 = release 5 = penetration

2, 5, 3, 1, 4

Select all of the following virus groups where the viruses use an enzyme called RNA-dependent RNA polymerase to complete their life cycle.

3 4 5

oose the proper order of the following events of the influenza virus life cycle.

3, 2, 1, 4, 5

Choose the proper order of the following events of the rotavirus life cycle.

3, 4, 1, 2, 5

Because the viral genome is negative strand DNA it can serve as the template for mRNA synthesis; this occurs during the S phase of the host cell's cycle.

Some of the mRNA produced encodes polypeptides that are needed for the unique parvovirus replication process. The ends of the genome are palindromes that fold back on themselves, forming a hairpin/polypeptide complex that the host DNA polymerase can use as a substrate.

Hemagglutinin found in the influenza virus functions to ________.

control the binding of the virus to host cell receptors

DNA-dependent DNA polymerase (DDDP)

DNA-dependent RNA polymerase RNA-dependent RNA polymerase RNA-dependent DNA polymerase PICTURE

Baltimore group VI viruses are the only viruses that use reverse transcriptases.

False

Which of the following statements is false regarding the function of reverse transcriptase in the life cycle of HIV?

Reverse transcriptase acts as a DNA-dependent RNA polymerase when it transcribes dsDNA to mRNA.

Once the nucleocapsid is released, it is transported to the host cell nucleus on microtubules.

The parvovirus genome then employs host cell enzymes to produce new viral material.

The reverse transcribing virus, Hepatitis B virus, will obtain its mature viral genome from _________.

a viral mRNA that has been reverse transcribed into DNA

The provirus state exists when

double-stranded viral DNA is integrated into host cell chromosome.

HIV leaves an infected cell by breaking down its cell membrane.

False

If the virus is present as a provirus in the host cell, it remains latent and never produces new virus.

False

Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside the bacterial cell.

False

Review the stages of the parvovirus B19 life cycle by completing each sentence.

Parvovirus B19 begins its life cycle by attaching to receptors on the surface of progenitors of red blood cells and enters the host cell via receptor-mediated endocytosis.

Which of the following viruses uses the rolling-hairpin model to replicate its nucleic acid? Parvovirus

RNA-dependent RNA polymerase is an enzyme that acts as a ________ by catalyzing the synthesis of viral mRNA. transcriptase

The major difference between RNA-dependent RNA polymerase (RdRp) and DNA-dependent RNA polymerase (DdRp) is that __________.

RdRp uses RNA as the template to make RNA, whereas DdRp uses DNA as the template to make RNA

Stress can activate the process of induction where the integrated phage genome is excised.

The excised genome becomes active and progression into the lytic cycle eventually leads to death of the host cell.

Bacteriophage lambda can enter either the lytic cycle or the lysogenic cycle and therefore is considered a temperate phage.

The start of its life cycle is similar to other bacteriophages, as it attaches to the host cell and injects its genome.

If it does not enter the lytic cycle, its dsDNA genome integrates into the host cell chromosome.

This process is catalyzed by the enzyme integrase at an attachment site and the genome remains in the chromosome as a prophage.

Attachment of HIV to a host cell requires a receptor and co-receptor on the surface of the host cell.

True

The polygenic mRNA codes for one long polyprotein that is cleaved into the separate individual virus proteins.

True

Viral lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.

True

Single-stranded RNA viruses containing RNA sequences that are complementary to the mRNA produced upon their infection of a host cell are called _______ RNA viruses.

minus-strand or negative-strand

A plus-strand RNA produced from a minus-strand RNA virus functions as a template for the production of ________.

negative-strand RNA genome

If the DNA of the provirus is transcribed ________.

one long polygenic mRNA is produced

In phage replication ________.

only the phage nucleic acid enters the bacterial cell

The causative agent of measles is a member of the Mononegavirales. Mononegavirales is a(n) ________ in terms of virus nomenclature.

order

In the attachment step of phage replication _________.

protein fibers in the phage tail attach to specific receptors on the bacterial cell wall

The process in TMV whereby translation of viral proteins continues beyond a stop codon is called ________.

readthrough

RNA-dependent RNA polymerase is an enzyme that acts as a ________ by catalyzing the synthesis of plus-strand RNA.

replicase