Microbiology Exam 2 Test Questions – Flashcards
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| About how many genes does a small virus have? A large virus? |
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| About 4-5; about 150-200 |
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| What do viruses consist of? |
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| A nucleic acid surrounded by a protein coat (a capsid) |
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| Which of the characteristics of viral nucleic that are true: Can be both DNA or RNA Double or single stranded Circular- cannot be linear Only comes in segments A matrix protein can surround the nucleic acid |
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| False True False False True |
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| What is the virus capsid made up of ? |
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| Made of protein subunits called capsomeres which fit together into a hollow shell |
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| What is the most common structures of a virus? |
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| An ocosahedron- 20 triangular faces |
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| What are other common structures of a virus? |
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| Polyhedral, helical, complex |
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| Some viruses have an outer membrane called _______________. |
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| Envelope |
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| Where does the virus envelope come from? |
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| Comes from the host cell membrane. |
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| True or False: The viruses envelope contains only viral proteins and glycoproteins in it. |
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| False, it can have both host and viral |
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| Why are these proteins important? |
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| These proteins are important because they can mediate adherence of the virus to the host, and can be antigenic (recognized as foreign by the host) and serve as vaccines. |
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| What part of a viruses structure attaches to receptors on the host and allow for infection? |
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| The protein spikes |
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| How many families of human viruses are there? |
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| 22- all ending with "viridae" |
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| What five features organize viral classification? |
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| 1. Nature of nucleic acid- RNA or DNA 2. Single-stranded or double-stranded nucleic acid 3. Capsid shape- polyhedral, helical, both 4. Presence or absence of an envelope 5. Size of virion |
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| How many families of DNA viruses currently exist? How many families of RNA viruses currently exist? |
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| 8;14 |
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| How are viral classification based on route of transmission grouped? |
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| Often grouped according to their route of transmission or organ system they infect |
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| How do enteric viruses spread and infect? |
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| Spread by the fecal-oral route, infect the GI tract |
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| How do respiratory viruses spread and infect? |
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| Spread by respiratory route, infect through the respiratory tract |
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| How do sexually transmitted viruses spread and infect? |
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| Spread through sexual transmission, infect through genital tract |
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| What are zoonotic viruses? |
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| Animal viruses that can infect humans |
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| What are arboviruses? |
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| Arthropod-borne, insect viruses that can infect humans. |
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| What does the virus genome contain? |
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| Only a few genes needed to make it capsomeres, replicate its nucleic acid, and get out of the host cell |
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| True or False: Viruses use host enzymes, ribosomes, and molecules to replicate |
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| True |
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| Explain the two-stage life cycle of viruses |
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| 1. Outside the host cell they are inert- virions 2. Inside the host cell they replicate themselves or to persist in a latent state until they begin replicating |
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| What is balanced pathogenicity? |
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| The virus may hurt the host a little but not enough to kill the host or reduce its ability to transmit the virus |
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| What is a productive infection? |
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| A virus that immediately invades, replicates, and kills their host cell |
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| What do latent viruses do? |
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| Viruses that integrate their chromosome into the host and stay latent until activated |
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| What is a persistent infection |
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| Viruses replicate slowly and continue to produce new viruses without immediately killing the host |
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| What are the steps in productive viral infections? |
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| 1. Attachment 2. Entry 3. Targeting 4. Uncoating of the virion 5 Viral DNA is transcribed, replicated and translated to make new viruses 6. New virions assemble or mature spontaneously 7. New viruses are released from the cell |
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| True or False: Viruses have a low host-range specificity for host species and organ tissues with the species |
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| False |
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| In bacteriophages, viral DNA is |
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| injected |
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| In animal viruses, the whole virus |
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| enters the host cell |
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| How do enveloped viruses enter its host? |
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| They fuse their membranes |
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| Where can targeting occur? |
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| Can be the cell cytoplasm or nucleus |
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| Where do most DNA viruses replicate? |
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| In the cell nucleus because that is where the deoxyribonucleotides and replication enzymes are |
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| What are the steps of uncoating of the virion? |
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| 1. The capsomeres open and release the nucleic acid for it to be replicated by the host cell's enzymes 2. Capsomeres are held together by weak hydrogen bonds |
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| What do the first enzymes do in viral DNA? |
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| Destroy the host genome to stop the cell from replicating |
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| What do later enzymes do? |
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| Replicate the viral genome and produce viral capsomeres |
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| True or False: Host metabolism continues, providing energy and components for the virus |
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| True |
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| What are the two types of acute viral infections? |
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| 1. Acute 2. Acute with noninfectious sequellae |
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| What are the two types of persistent viral infections? |
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| 1. Latent 2. Chronic |
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| What are the types of viral infections? |
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| 1. Slow viruses 2. Prions 3. Retrovirus |
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| What are the characteristics of a slow virus? |
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| -Following a mild or subclinical acute infection, the virus gradually increases its replication and pathology over months, years, or decades |
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| What are prions and what are their characteristics? |
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| Prions are infectious agents that we associate with protein sequences but no nucleic acids. They cause CNS disease in animal and humans |
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| What are the characteristics of a Retrovirus? |
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| 1. Named for an enzyme, reverse transcriptase 2. Causes acquired immunodeficiency syndrome (AIDS) in humans 3. The entire virus genome is translated as one protein, the cleaved by a protease 4. Anti-HIV drugs are inhibitors of the viral protease |
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| What are oncogenes |
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| When DNA viruses become latent and integrate their DNA into the genes of humans, they can transform the cells and cause uncontrolled growth. |
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| What type of virus prefers stability |
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| Latent virus |
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| What type of virus prefers instability? |
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| If the virus needs to stay ahead of the host immune system, instability may be good because the virus can change before the immune system catches up |
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| What are cells in living host tissues separated with? |
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| Trypsin |
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| What is contact inhibition? |
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| When cells divided until they touch, then stop |
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| How do you passage a flask that is full? |
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| Remove the cells trypsin, dilute them, feed them, and put them in a new flask or tube |
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| What are primary cell cultures? |
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| The cells made directly from the tissues |
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| What are immortal cells? |
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| Cell lines that keep dividing |
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| What are the advantages of using culture? |
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| 1. Culture of the virus from the specimen is the definitive way to diagnose a viral infection 2. You can do further tests to characterize it and save it |
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| What are the disadvantages of culture? |
answer
| 1. Cultures take a long time and cost a lot 2. Requires a separate lab 3. Requires a lot of skill and equipment |
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| What is Direct Flourescent Antibody (DFA) testing? |
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| 1. Detects virus- specific antigens on the host cell 2. Take the direct specimen with infected cells it in, put them on a microscope slide, stain 3. If the cell lights up, they are infected |
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| What does an amplified nucleic acid test detect? |
answer
| Specific segments of the virus nucleic acid. |
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| What are the advantages of PCR? |
answer
| 1. Sensitivity; can detect one copy of the virus 2. Specificity; if you chose your primers well 3. Can be fast; 2-3 hours |
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| What are the disadvantages of molecular tests? |
answer
| 1. Can't tell live from dead virus 2. Useless for persistent viruses; it is always there |
question
| How do sexually transmitted viruses spread and infect? |
answer
| Spread through sexual transmission, infect through genital tract |
question
| What are zoonotic viruses? |
answer
| Animal viruses that can infect humans |
question
| What are arboviruses? |
answer
| Arthropod-borne, insect viruses that can infect humans. |
question
| What does the virus genome contain? |
answer
| Only a few genes needed to make it capsomeres, replicate its nucleic acid, and get out of the host cell |
question
| True or False: Viruses use host enzymes, ribosomes, and molecules to replicate |
answer
| True |
question
| Explain the two-stage life cycle of viruses |
answer
| 1. Outside the host cell they are inert- virions 2. Inside the host cell they replicate themselves or to persist in a latent state until they begin replicating |
question
| What is balanced pathogenicity? |
answer
| The virus may hurt the host a little but not enough to kill the host or reduce its ability to transmit the virus |
question
| What is a productive infection? |
answer
| A virus that immediately invades, replicates, and kills their host cell |
question
| What do latent viruses do? |
answer
| Viruses that integrate their chromosome into the host and stay latent until activated |
question
| What is a persistent infection |
answer
| Viruses replicate slowly and continue to produce new viruses without immediately killing the host |
question
| What are the steps in productive viral infections? |
answer
| 1. Attachment 2. Entry 3. Targeting 4. Uncoating of the virion 5 Viral DNA is transcribed, replicated and translated to make new viruses 6. New virions assemble or mature spontaneously 7. New viruses are released from the cell |
question
| True or False: Viruses have a low host-range specificity for host species and organ tissues with the species |
answer
| False |
question
| In bacteriophages, viral DNA is |
answer
| injected |
question
| In animal viruses, the whole virus |
answer
| enters the host cell |
question
| How do enveloped viruses enter its host? |
answer
| They fuse their membranes |
question
| Where can targeting occur? |
answer
| Can be the cell cytoplasm or nucleus |
question
| Where do most DNA viruses replicate? |
answer
| In the cell nucleus because that is where the deoxyribonucleotides and replication enzymes are |
question
| What are the steps of uncoating of the virion? |
answer
| 1. The capsomeres open and release the nucleic acid for it to be replicated by the host cell's enzymes 2. Capsomeres are held together by weak hydrogen bonds |
question
| What do the first enzymes do in viral DNA? |
answer
| Destroy the host genome to stop the cell from replicating |
question
| What do later enzymes do? |
answer
| Replicate the viral genome and produce viral capsomeres |
question
| True or False: Host metabolism continues, providing energy and components for the virus |
answer
| True |
question
| What are the two types of acute viral infections? |
answer
| 1. Acute 2. Acute with noninfectious sequellae |
question
| What are the two types of persistent viral infections? |
answer
| 1. Latent 2. Chronic |
question
| What are the types of viral infections? |
answer
| 1. Slow viruses 2. Prions 3. Retrovirus |
question
| What are the characteristics of a slow virus? |
answer
| -Following a mild or subclinical acute infection, the virus gradually increases its replication and pathology over months, years, or decades |
question
| What are prions and what are their characteristics? |
answer
| Prions are infectious agents that we associate with protein sequences but no nucleic acids. They cause CNS disease in animal and humans |
question
| What are the characteristics of a Retrovirus? |
answer
| 1. Named for an enzyme, reverse transcriptase 2. Causes acquired immunodeficiency syndrome (AIDS) in humans 3. The entire virus genome is translated as one protein, the cleaved by a protease 4. Anti-HIV drugs are inhibitors of the viral protease |
question
| What are oncogenes |
answer
| When DNA viruses become latent and integrate their DNA into the genes of humans, they can transform the cells and cause uncontrolled growth. |
question
| What type of virus prefers stability |
answer
| Latent virus |
question
| What type of virus prefers instability? |
answer
| If the virus needs to stay ahead of the host immune system, instability may be good because the virus can change before the immune system catches up |
question
| What are cells in living host tissues separated with? |
answer
| Trypsin |
question
| What is contact inhibition? |
answer
| When cells divided until they touch, then stop |
question
| How do you passage a flask that is full? |
answer
| Remove the cells trypsin, dilute them, feed them, and put them in a new flask or tube |
question
| What are primary cell cultures? |
answer
| The cells made directly from the tissues |
question
| What are immortal cells? |
answer
| Cell lines that keep dividing |
question
| What are the advantages of using culture? |
answer
| 1. Culture of the virus from the specimen is the definitive way to diagnose a viral infection 2. You can do further tests to characterize it and save it |
question
| What are the disadvantages of culture? |
answer
| 1. Cultures take a long time and cost a lot 2. Requires a separate lab 3. Requires a lot of skill and equipment |
question
| What is Direct Flourescent Antibody (DFA) testing? |
answer
| 1. Detects virus- specific antigens on the host cell 2. Take the direct specimen with infected cells it in, put them on a microscope slide, stain 3. If the cell lights up, they are infected |
question
| What does an amplified nucleic acid test detect? |
answer
| Specific segments of the virus nucleic acid. |
question
| What are the advantages of PCR? |
answer
| 1. Sensitivity; can detect one copy of the virus 2. Specificity; if you chose your primers well 3. Can be fast; 2-3 hours |
question
| What are the disadvantages of molecular tests? |
answer
| 1. Can't tell live from dead virus 2. Useless for persistent viruses; it is always there |
