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Chapter 26: Virus
Key terms and important information
| Question | Answer |
|---|---|
| Virus | Infective agent consisting of nucleic acids in a protein coat. Can only multiply within living cells of a host |
| Reverse Transcriptase | Reverse Transcriptase: Process in cells where an enzyme makes copy of DNA from RNA |
| Envelop | Combo of cell membrane, cell wall, and outer membrane (if present) |
| Host Range | Types of organisms infected |
| Tissue Tropism | Inside a host, the virus may only infect certain tissues |
| Retrovirus | An RNA virus with reverse transcriptase enzyme |
| Giant viruses | Very large virus; sometimes bigger than bacteria |
| Baltimore structure | Classification system placing viruses into groups depending on combination of NA (DNA or RNA), strandedness (single or double-stranded), sense(+/-), method of replication |
| Metagenomics | Study of the structure/function of entire nucleotide sequences isolated and analyzed in bulk samples. Used to study specific communities of microorganisms by use of environmental sample, amplification, sequencing and comparing to database |
| + RNA | Cellular ribosomes translate to protein; virus delivers enzyme to make DNA copy from RNA |
| – RNA | Virus delivers enzyme to make + RNA & and reverse transcriptase |
| Bacteriophage AKA Phage | Viruses that infect bacteria |
| Lytic reproductive cycle | - Hijacks host cell - Makes new phages using cell’s resources - Causes cell to burst and die |
| Lysogenic reproductive cycle | - Dormant/Latent stage - Integration of virus NA into host genome, letting virus and cell’s DNA replicate - Integrated genome (prophage); cell containing prophage called lysogen - Some viral genes may be expressed |
| Antigenic shift | Accumulation of a series of minor genetic mutations |
| Antigenic drift | Mixing of genes from influenza viruses from different species - make previous vaccines no longer protective. Can cause pandemics |
| Coronavirus (MERS-CoV, SARS-CoV, SARS-CoV-2) | - Range of morbidities 💀- - Some are asymptomatic - Respiratory tract symptoms - Neurological symptoms - Acute respiratory distress, pneumonia, kidney failure, death - Ground glass lung, brain fog (Long term) |
| IFR (Infection-to-fatality ratio) | Low for children, high for elderly (For Covid) |
| Opportunistic infections | Infections that normally don’t cause serious damage |
| Viroid | Small naked circular RNA molecules; cause disease in economically important crops ○ Small interfering RNA’s (siRNAs) may be produced during infection; interfere with plant growth/development |
| The switch from a lysogenic prophage to a lytic cycle is called | Induction |
| A mutation in the gene encoding the integrase enzyme renders the protein non-functional. How would this affect the HIV infection cycle? | The viral DNA would not be able to integrate the viral genome into a chromosome |
| Each HIV particle possesses a _________ on its surface, called gp120, that precisely binds to a protein, called CD4, that is found on the surfaces of the immune system cells called macrophages and T cells. | Glycoprotein |
| If a researcher developed a drug that prevented insertion of the SARS-CoV-2 spike protein into the endoplasmic reticulum, what effect would you predict from this drug? | The viral particles produced could not infect new cells. |
| MERS-CoV, SARS-CoV, and SARS-CoV-2 are members of the family of viruses called ________. | Coronavirus |
| The pneumonia caused by the influenza virus results from the accumulation of fluid and cell debris in the lungs. This occurs during the lysogenic life cycle of the virus (TRUE/FALSE) | False |
| Once a prophage is present in a bacterial genome, viral genes are reproduced every time the bacterium multiplies. Expression of viral genes is inhibited by a repressor protein. Cell stress can induce the formation of proteases that degrade. Therefore... | The virus will enter the lytic cycle |
| Viruses that become established as stable parts of the host cell genome are called | temperate |
| Viruses are ________ -coated fragments of DNA | protein |
| Plasma from a sick mouse is filtered across a membrane that has a 200 nm pore size. If the filtrate is still infectious when injected into a healthy mouse, then the pathogen is most likely a(n): | virus |
| Scientists have demonstrated that the cholera bacteria, Vibrio cholerae, can exist as a rather harmless form or as a disease-causing form? What causes the switch? | A phage introduces a toxin gene into the bacterium's chromosome. |
| What kind of pathogen would retain its ability to cause infections after being treated with powerful proteolytic chemicals that would destroy all proteinaceous material? | A viroid |
| Viruses are self-replicating but the replication is much faster in a host cell. (TRUE/FALSE) | False |
| Vibrio cholerae lives in water and gets toxin genes from a virus by phage conversion. The toxin results in massive diarrhea. Untreated cholera has about a 50% mortality rate. How do the bacteria benefit? | Diarrhea helps the bacteria to spread from person to person. |
| Why do retroviruses need to contain the enzyme reverse transcriptase? | Because host cells' genomes do not contain a gene encoding an enzyme that can make DNA from RNA |
| What is the most reasonable explanation for why a bacteriophage capable of infecting E. coli would be unable to infect a human lung epithelial cell? | The receptors to which the bacteriophage attach on E. coli are not found on lung cells |
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