Micro Test 5 (HW)

Acute infections in animals: 1 - are a result of productive infection 2 - generally lead to long-lasting immunity 3 - result from integration of viral nucleic acid into the host 4 - are usually followed by chronic infections 5 - often lead to tumor formation

1 and 2

All phages must be able to: 1 - inject their nucleic acid into a host cell 2 - kill the host cell 3 - multiply in the absence of living bacteria 4 - lyse the host cell 5 - have their nucleic acid replicate in the host cell

1 and 5

What is the role of prophages in persistent infections?

A prophage results from integration of the genetic matrial of a bacteriophage into the bacterial chromosome; this can lead to long lasting bacterial changes such as lysogenic conversion.

What is the role of proviruses in persistent infections?

A provirus is a viral genome integrated into the host animal cell DNA; in persistent infections it may remain silent for long periods of time then reactivate and trigger infectious disease again.

What is the difference between acute and persistent infection?

Acute infections have rapid onset, short duration and symptoms are due to host cell death and immune system involvement, while persistent infections remain for long periods of time (years and even lifetime) and can be chronic or latent.

What is lysogenic conversion?

Change in the phenotype of a lysogen as a consequence of specific prophage integration

Why are RNA viruses more error-prone in their replication than DNA viruses?

DNA viruses replicate with host DNA polymerase which has proofreading activity; RNA viruses require replicase or reverse transcriptase enzymes that do not have proofreading activity.

How is specialized transduction different from generalized transduction?

Specialized transduction results from an excision mistake during transition of lysogenic to lytic cycle of a temperate phage, where a short piece of flanking bacterial DNA is removed. Generalized transduction results from packaging errors therefore any existing fragments of bacterial DNA can be packaged.

How is the replication cycle of the lambda phage different from that of T4?

T4 is lytic or virulent while lambda is a temperate phage that can lead to lytic or lysogenic infection

Filamentous phages

are extruded from the host cell

The tail fibers on phages are associated with

attachment

Why are non-enveloped viruses generally more resistant to disinfectants than enveloped viruses?

because disinfectants can destroy the lipid envelope but not always the protein coat

Why must a (-) strand but not a (+) strand RNA virus bring its own replicase into a cell?

because the (+) RNA strand can be used as mRNA to immediately translate the replicase, but not the (-) RNA strand

Temperate phages can do all of the following except

bud from their host cells

Prions

cause diseases of humans

Influenza vaccines must be changed yearly because the amino acid sequence of the viral proteins changes gradually over time. Based on this information, which is the most logical conclusion? The influenza virus

has an RNA genome

How do prions propagate?

it is thought that a misfolded prion protein has the ability to induce misfolding of normal counterparts of the protein, thus generating more prions

Capsids are composed of

protein

COVID-19 can be detected with a PCR test that amplifies viral nucleic acids. If you experience flu-like symptoms (or worse) you should see a doctor and get tested right away.

true

COVID-19 is caused by a zoonotic virus

true

COVID-19 is caused by an enveloped virus, which means that washing hands frequently with water and soap can significantly eliminate the virus.

true