MICR-4160 Lecture Notes - Lecture 1: Intracellular Parasite, Rna Virus, Virome

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2 Sep 2019

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Virus: an infectious obligate intracellular parasite comprising of genetic material surrounded by a protein coat or sometimes a membrane. The genetic material can either be rna or dna. There are two types of viruses: naked or enveloped. The naked viruses are harder to kill because there is no envelope to damage. All viruses must make mrna that can be translated by the host"s ribosomes. They are parasites of hosts protein synthesis machinery. 1-1. 5% of our genome contains protein-coding genes while 8-10% of our genome is viral. We regularly eat and breathe a bunch of viral particles. Viruses are essential for running biogeochemical cycles. The structure of viruses break down outside of the host"s bodily fluids and some viruses can be apart of you for life. Retrovirus: takes rna and turns it into dna. the genetic material is then incorporated into the host genome and stays there forever. (ex. Mnv. an enteric virus that reverses intestinal abnormalities in gf mice)

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QUESTION 1: The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by __________________________.

A. the helical shape of its viral capsid

B. the type of nucleic acid used for its viral genome (single-stranded, antisense RNA)

C. the spikes that protrude from its viral envelope

D. the segmented nature of its viral genome

QUESTION 2: Which of the following genome types has been observed in viruses? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.

A. Single-stranded RNA

B. Single-stranded DNA

C. Double-stranded RNA

D. Protein-based

QUESTION 3: Choose the correct statement about viral evolution.

A. RNA and DNA viral genomes evolve at equal rates.

B. Cellular genomes mutate at a faster rate than viral genomes due to their large size and increased chance of replicative mistakes.

C. DNA viruses mutate faster than RNA viruses because thymine is more susceptible to mutation than uracil.

D. RNA viruses mutate faster than DNA viruses due to a lack of proofreading replicative enzymes.

QUESTION 4: Your elderly patient is affected by shingles. After careful observation, you note that the virus responsible for the infection has an icosahedral capsid, is enveloped, and has double-stranded linear DNA as its genetic material. Based on this information, in which of the following viral families would you group this viral pathogen?

QUESTION 5: Which of the following is a key difference between lytic and lysogenic bacteriophage replication cycles?

A. Lysogenic bacteriophages release via host cell lysis, whereas lytic bacteriophages bud off from the host cell membrane.

B. The lytic replication cycle ends with host cell lysis and release of newly formed bacteriophage particles, whereas lysogenic replication leads to prophage formation.

C. Lytic replication requires an uncoating step, whereas in lysogenic replication, the bacteriophage's nucleic acid is directly injected into the host cell.

D. Whereas lytic replication enables the infection of several hosts, lysogenic replication only allows for infection of a single host cell.

QUESTION 6: Which of the following is an unsuitable culture method for an animal virus?

A. Direct inoculation of virus onto blood agar

B. Live animal inoculation

C. Tissue culture method

D. Injection of virus into embryonated eggs

1. Unlike Ebola virus, SARS virus
a. has large spikes that look like a âcrownâ.
b. is enveloped.
c. is helical.
d. is in the family Togaviridae.
e. is a ssRNA virus.

2. Which virus or virus family is described in the followingpassage?
Electron micrographs of the hemagglutinin subunits (in the presenceof SDS) showed
rods approximately 40 Ã wide and 140 Ã long. The neuraminidasesubunits had a quite
different appearance. In the presence of SDS, these were seen asoblong structures about 85 Ã long and 50 Ã wide with a centrallyattached fibre 100 Ã long possessing what appeared to be a diffusetail or small knob about 40 Ã in diameter at its end.1
a. Togaviridae
b. Epstein-Barr virus
c. Smallpox virus
d. Orthomyxoviridae
e. Filoviridae
f. Rabies virus

3-Following is a passage from the New England Journal ofMedicine:
______________________ is an exclusively human herpesvirus that ...becomes latent in
cranial-nerve and dorsal-root ganglia, and frequently reactivatesdecades later to produce shingles and postherpetic neuralgia. Inimmunocompetent elderly persons or
immunocompromised patients, ____________________ may producedisease of the central nervous system.
This passage refers to which virus?
a. West Nile virus
b. Smallpox virus
c. Epstein-Barr virus
d. Ebola virus
e. Varicella-zoster virus

4. Pneumoviruses can cause colds and pneumonia in humans. They aresingle-stranded,
negative-sense, nonsegmented RNA viruses. These enveloped virusesare surrounded by an envelope that is characterized by fusionglycoproteins and host-derived proteins. With this knowledge, it islikely that pneumoviruses
a. enter host cells via endocytosis.
b. leave host cells by budding.
c. enter host cells via membrane fusion.
d. A and B
e. B and C

5. Recall that poliovirus is a positive-sense (+) ssRNA virus. The5â Ã ? 3â strand of RNA,
once uncoating has taken place, can serve as an mRNA and encode forviral proteins.
However, in order for the virus to create more +ssRNA to package indaughter viruses, it must
a. generate a dsRNA molecule that can encode for the synthesis ofmore +RNA.
b. integrate into the host cell DNA.
c. utilize an RNA-dependent DNA polymerase to make aheteroduplex.
d. undergo reassortment
e. All of the above

6. Some influenza hosts, such as humans and pigs, cansimultaneously contract human,
avian and swine influenza viruses at the same time. What can occurduring the maturation phase of virus replication in such ahost?
a. Reassortment
b. RNA of all three sources: human, swine and avian, can bepackaged into a single
virion.
c. Genetic shift
d. All of the above

7. The HIV virion contains enzymes/proteins that do all of thefollowing EXCEPT
a. An enzyme that creates âDNA using +RNA as template.
b. A protein that serves as a chemokine receptor.
c. A DNA-dependent DNA polymerase.
d. An enzyme that allows +/- viral DNA to be spliced into the hostcellâs DNA.
e. A protein that mediates membrane fusion.

8. After a long series of biochemical tests, Kyle and Matt werefinally able to identify their Gram-negative unknowns asPseudomonas aeruginosa and Shigella dysenteriae,
respectively. As they compare notes, they realize that theirunknowns are in the
___________ Pseudomonadaceae and Enterobacteriaceae, respectively.However, they also note that both of their unknowns are in the______________ ? proteobacteria.
a. genera, species
b. phyla, family
c. families, class
d. order, phyla
e. classes, order

9-Hydrogenobaculum acidophilum is a resident of YellowstoneâsNorris Geyser basin. This thermoacidophilic microbe grows instringy, white mats and is a member of the phylum Aquificae.Hydrogenobaculum acidophilum
a. could be further researched in Volume 2 of Bergeyâs Manual ofSystematic
Bacteriology.
b. is in the domain Archaea.
c. is a deeply branching bacterium.
d. is a proteobacterium.
e. All of the above

10-After talking about the Group A Streptococci (GAS) and theircapability to sometimes cause a flesh-eating disease callednecrotizing fasciitis, Derek decides to research this group a bitmore. As he reads, he quickly learns that
a. they are microaerophilic Gram-negative rods.
b. they are in the phylum ?-proteobacteria.
c. they are found Volume 4 of Bergeyâs Manual of SystematicBacteriology.
d. they have less than 50 mol % GC content.
e. none of the above

MICR-4160 Lecture Notes - Lecture 1: Intracellular Parasite, Rna Virus, Virome

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