Exam 2 All Flashcards Hopefully

\________________are small, acellular infectious agents that are considered nonliving.

viruses

Can viruses synthesize their nucleic acids and proteins apart from their host?

No

Viruses called \___________________ pathogens-disease-causing microbes must invade living cells and hijack their biochemical and cellular tools to replicate.

obligate intracellular

What is a virus that infects bacterium called?

bacteriophages

A single infectious virus particle is called a \________.

virion

What is a capsid and what macromolecule makes up a capsid?

The protein shell that packages and protects the genome and also accounts for the bulk of a virion’s mass.

Three-dimensional sunbits whose arrangement determines a capsid’s shape are called \_________________.

capsomeres

List general virus capsid shaoes,

helical capsid, icosahedral capsid, complex structure

What capsid shape is the SARS-COV-2 virus?

Icosahedral capsid

What macromolecule makes up a viral envelope?

lipid

What is a “naked” virion?

Describes the ones that lack envelopes.

Where does an enveloped virus obtain its envelope?

Budding from the host, taking a portion of the cell membrane with them as a coating when they go.

What is another term for viral spikes?

peplomers

What macromolecule makes up viral spikes?

glycoprotein

Viral \___________ bind to specific factors on a host cell which determines the exact cell type a virus can infect.

spikes

The influenza virus that causes swine flu is called H1N1. Name the glycoproteins that produce “HA” and “NA” spikes, which are represented by H and N, respectively in H1NI.

hemagglutinin and neuraminidase

RNA; DNA

In general, viral genomes can either be \________ or \__________, but usually not both.

Which type of single-stranded RNA virus genome functions directly as mRNA?

ssRNA+

What enzyme is used by single-stranded antisense RNA (ssRNA-) viruses to make mRNA from an RNA template?

RNA-dependent RNA polymerases

The enzyme \____________ makes DNA from an RNA template.

reverse transcription

RNA viruses mutate more quickly than DNA viruses because RNA polymerases do not have the \__________ capabilities that DNA polymerases do.

proofreading

Do attenuated virus strains cause disease in healthy, non-immunocompromised hosts?

No, but they do stimulate immune response.

Define tropism.

The preference of the pathogen for a specific host (and even specific tissue within the host).

What is antigenic shift?

Minor genetic changes in a virus; leads to influenza outbreaks.

How does an antigenic shift influence influenza?

Leads to outbreaks.

What is antigen shift?

Major genetic reassortment that dramatically changes the virus; often leads to viral strains with new features.

How does antigen shift influence influenza?

Leads to pandemics.

List the properties that are used for classifying viruses?

Type of nucleic acid present (DNA or RNA), capsid symmetry (helical, icosahedral, or complex), presence or absence of an envelope, genome architecture (ssDNA, ssRNA, etc.).

Name the immunization strategies for SARS-CoV-2 vaccines,

mRNA vaccinations and vector vaccines

The Pfizer and Moderna SARS-CoV2- vaccines use which immunization strategy?

mRNA vaccines

What viral protein is coded by Pfizer and Moderna SARS-Co-V-2 vaccines, which is then produced by the host?

The mRNA in the vaccine is coated in lipids that help the patient’s cells take up the mRNA so it’s transferred to make a segment of it.

The Johnson and Johnson SARS-CoV-2 vaccine use which immunization strategy?

vector vaccine approach

Do the SARS-CoV-2 vaccine produced by Pfizer, Moderna, or Johnson and Johnson change your DNA? Why or why not?

No, because the mRNA sequence can’t be incorporated in human chromosomes.

Define host range.

The collection of species that a pathogen can infect.

Certain viruses like Ebola, are said to have a broad tropism. What does that mean?

Can infect a wide range of host cells or tissues.

Viruses are not classified into domains, but their highest taxonomical classification is kingdom.

phylum level

In bacteriophage, \________ replication kills the host cell when new phage is released.

lyptic

List the steps of lytic replication in the order they occur, and briefly describe what occurs during each step.

(1) Attachment: bacteriophage tail fibers help the virus adhere to specific proteins on the bacterial cell wall surface, bacteriophages only infect certain bacteria. (2) Penetration: bacteriophage injects genetic material into the cell, through the host’s cell wall and plasma membrane. (3) Replication: bacteriophage commandeers host cell factors to transcribe and translate vital genes, viral genome also encodes proteins to build new phage particles and enzymes that will copy the viral genome. (4) Assembly: after bacteriophage replication, viral factors pack the viral genome into the capsid with the remaining phage parts assembled to build completed virions. (5)Release: bacteriophage encodes lysosome which breaks host cell walls and causes bacterial bursting once newly assembled phages are mature. Once released they can infect other cells.

During lysogenic replication of a temperate bacteriophage, a \_________ is formed when the phage genome is incorporated into the host cell’s genome.

prophage

When would temperature phages, such as lambda phages, revert from a lysogenic pathway to a lytic pathway?

If a host cell carrying a prophage is stressed, the prophage may exercise itself from the host genome and enter the other pathway.

What is the medical importance of phage conversation?

Their ability to confer new pathogenic properties to bacterial cells.

List the steps of animal virus in the order they occur and briefly describe what occurs in each step.

(1) Attachment: Vital surface proteins interact with host plasma membrane proteins. (2) Penetration: Occurs by fusion or endocytosis. (3) Uncoating: Genome released from capsid. (4) Replication: Genome is replicated and viral proteins made. (5) Assembly: New virions are assembled. (6) Release: Virions are released by budding or lysis.

Define acute infection.

Viruses that employ the productive infection replication strategy cause this. They run their course and are cleared by the host immune system.

Define persistent infection.

Chronic or latent infections caused by persistent viruses that tend to remain in the host for long periods-from many weeks to a lifetime.

Certain animal viruses that cause chronic infections incorporate their genome into the host cell’s genome to form a \______.

provirus

What is one of the most important advances in HIV treatment for healthcare providers who may have been exposed to HIV?

Post exposure prophylaxis (PEP), or preventing the infection from starting.

\_________ infections differ from chronic persistent infections by their characteristic flare-ups with intermittent periods of dormancy.

latent

Human herpes virus-1 (HHV-1, also known as HSV-1) is known to lie dormant in host nerve cells and then reemerge to generate \________.

cold sores

The \__________ virus (HHV-3) causes chickenpox but remains latent in host nerve cells. It can reemerge and cause \___________.

varicella-zoster; shingles

Viruses that cause persistent infections and are often associated with cancer are called \_______________.

oncogenic viruses

U.S. Centers for Disease Control and Prevention (CDC) reports that about ________ percent of all cervical cancers are linked to HPV.

90

Which retroviruses form proviruses and can quietly persist host cells for more than a decade before emerging to cause leukemia or lymphoma?

HTLV-1 and HTLV-2

Define plaque.

A clear zone after lytic bacteriophages lyse out the host cell at the end of their replication pathways and kill the host cell. Represents a single bacteriophage in the initial sample.

List the general ways that viruses can be grown in the laboratory.

Using tissue culture techniques, primary cell lines derived directly from the preferred host, and embryonated eggs (usually fertilized chicken eggs).

What is a concern when vaccines are made from virions purified from fertilized chicken eggs?

Miniscule amounts of egg protein will remain in the purified viral preparation, people allergic to eggs can’t be vaccinated with this type of vaccine.

Define specificity in reference to diagnostic testing methods.

Detects only the agent of interest without producing false positive results.

Define sensitivity in reference to diagnostic testing methods.

Describes the ability of the diagnostic test to detect very low levels of the target to limit false negatives.

You are testing a patient’s blood using an agglutination test. Latex beads are coated with antibodies that are specific to human immunodeficiency virus (HIV). When the beads and blood are mixed, agglutination occurs. What does this test indicate?

The sample contains the virions being sought.

You are testing a patient’s blood using an agglutination test. Latex beads are coated with herpes virus-1 virions. When the beads are mixed no agglutination occurs. What does this test indicate?

There is a negative result for virus.

What type of immune assay adheres an antigen or antibody to a surface and usually changes color if binding occurs?

Enzyme linked immunosorbent assay (ELISAs)

A technique called \____________ amplifies specific regions of genetic material.

polymerase chain reaction (PCR)

Any step in the viral \___________ pathway can be potential drug targets.

relication

When developing drugs what is selective toxicity and why is it important?

It stops the pathogen but leaves the host cells behind without this it would be poison.

What categories of testing options are currently used to detect active SARS-CoV-2 infections?

reverse transcription PCR tests and antigen tests

What does the RT-PCR test detect?

Detects a specific genetic sequence of SARS-CoV-2, the etiological agent of COVID-19. SARS-CoV-2 is a ssRNA+ virus. The reverse transcriptase makes a DNA copy of the RNA, then the DNA is amplified using certain reagents that will only allow the amplification of specific SARS-CoV-2 sequence. The \n presence of the sequence in the sample determines if you have the virus.

What does an antigen test detect?

The genetic material of SARS-CoV-2. Viral antigen using rapid detection assay (rapid lateral flow immunoassay) in a cartridge form. For most commercially available at home or in clinic rapid detection assays (such as, but not limited to Flowflex™ by ACON Laboratories, BinaxNOW™ by Abbott Labs, etc...).

How to use an antigen test?

A nasal swab sample is collected and is mixed with a solution that lyses cells releasing any virions. The test solution is added to a test strip that contains detector antibodies and antibodies that will specifically bind to nucleocapsid protein antigens from SARS-CoV-2. If antigen is present, the antibodies on the text strip will bind it, causing a color change on the strip. If the sample is positive, a line will appear next to the test lane.

Which test is most sensitive/ “gold standard” test when detecting SARS-CoV-2 infection?

RT-PCR

\___________ analogs are drugs that block nucleic acid replication.

Nucleoside

A nucleoside analog called \_____________ blocks DNA replication in cells infected with HHV-1, or varicella-zoster virus (HHV-3).

acyclovir

Human immunodeficiency virus (HIV), the etiological agents of AIDS is a retrovirus. What would be the best choice of drugs that would specifically inhibit making a DNA copy of the HIV genome?

Nucleoside reverse transcription inhibitors

Viral replication can be locked by short sequences of nucleotides that are complementary to the RNA transcribed by specific viruses called \____________.

antisense antivirals

Tamiflu is used to treat Influenza A. What mode of action does Tamiflu use?

Viral release, it prevents certain viruses from budding off the host surface cell.

\_____ are proteinaceous infectious particels.

prions

Viruses and prions are both acellular infect agents. List the main differences between viruses and prions.

The first has genetic material and can replicate unlike the second one which doesn’t have genetic material and can’t replicate.

Prions cause a class of diseases called \______________.

spongiform encephalopathies

What is the current theory about how normal prion proteins become misfolded?

The infectious version makes contact with the normal version, causing changes to the normal protein’s shape. This leads to chain reaction of that spreads throughout the brain’s prion proteins. As the misshapen ones clump together they cause brain tissue degeneration through an unknown mechanism.

Why are diseases caused by prions called spongiform diseases?

As the brain tissue deteriorates spongy holes are left in the tissue.

Name the spongiform diseases that are caused when a child inherits a parental gene that encodes a mutated form of the prion protein,

Gerstmann-Straussler-Scheinker syndrome and fatal familial insomnia.

Which type of acquired Creutzfeld-Jakob disease (CJD) has been given the name “mad cow disease”?

Variant CJD

What type of acquired CJD is caused by accidental transmission to a patient as a result of medical intervention?

Iatrogenic CJD

Several neurodegenerative diseases have been associated with misfolded proteins in the brain but are not considered spongiform encephalopathies. List them.

Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS)

Most prokaryotes divide using an asexual process called \______________.

binary fission

Certain fungi and some bacteria divide using an asexual process called \______.

budding

How many bacteria would be present after 3 hours if you start with a single bacterium that can divide every 30 minutes?

64

List the phases of bacterial growth and briefly describe what occurs in each.

Phase 1 Lag Phase: Cells alter their gene expression to their new setting. Phase 2 Log Phase: An upward slope line that results when the number of viable cells is plotted on a logarithmic scale as a function of time; occurs until nutrients sufficient and waste not appreciably accumulating. Phase 3 Stationary Phase: Population growth rate slows number of dying cells matches number of cells dividing, lasts as long as cells divide and nutrients available. Phase 4 Death Phase: Waste buildup and decreasing nutrients reach a critical point and cells begin to die it’s exponential varies on starting factors and species being grown.

List the main temperature groups and the ranges they grow in?

Psychrophiles -20 to 10 C; Psychrotrophs 0 to 30 C; Mesophiles 10 to 50 C; Thermophiles 40 to 75 C; Extreme thermophiles 65 to 120 C

List the names and pH ranges for prokaryotes grouped by pH requirements.

Acidophiles can grow at pH 1 or less to 5 and live in areas like sulfur sprngs and volcanic vents. Neutralophiles grow best at pH 5 to 8. Alkaliphiles pH range 9 to 11 and they live in extremely basic pH conditions like soda lakes..

What type of bacteria would you expect to find living in the Great Salt Lake of Utah?

halophiles

\___________ are organisms that live in extreme pH, temperature, or salt concentration ranges.

extremophiles

Many aerobic bacteria remediate reactive oxygen species (ROS) using enzymes that convert the reactive intermediates into nonreactive products. The enzyme \__________ converts superoxide to hydrogen peroxide (H2O2), then the enzyme \____________ converts H2O2 into oxygen and water.

superoxide dismutases; catalase

The degree to which an organism can detoxify reactive oxygen species (ROS) is directly related to how much oxygen it can tolerate. Which of the following organisms do you think has no ability to detoxify ROS?

obligate anaerobe

heterotrophs; autotrophs

There are two categories of organisms based on how they obtain organic carbon. ___________require an external source of carbon such as carbohydrates, lipids, and proteins, and ___________ “fix” inorganic carbon into organic carbon.

phototrophs; chemotrophs

Organisms that use light for energy are \________ and organisms that break down chemical substances are called \_______.

List the physical states of growth media and state the main use for each.

Liquid formats are ideal for large batches of microbes and to study certain metabolic processes. Solid is useful for isolating colonies and observing specific culture characteristics. Also to isolate bacteria into cultures using the streak plate technique. Semisolid is used for motility test to determine if an isolated specimen is able to move.

defined; complex

\________ media’s composition is precisely known, whereas \_________ media’s composition is not exactly known.

\_________ media is specifically formulated, so that certain microbes can be visually distinguished from other based on how they metabolize media components.

differential

\________ agar is a differential media that differentiates between microbes that cannot lyse red blood cells, and the extent in which they can do so.

blood

Which type of hemolysis depicts complete lysis of red blood cells?

beta hemolytic

Mannitol salt agar (MSA) is a selective and differential media. What kind of organism does MSA select for?

Bacteria that tolerate high salt levels.