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Viruses
| Question | Answer |
|---|---|
| describe basic features of viruses | extremely common; super tiny; noncellular, parasitic entities (cannot be classified in a kingdom and can affect any living thing); incredibly diverse (one virus can affect several or one species) |
| what structures do have viruses have? | all viruses have: genetic material (DNA or RNA); capsid (proteins that enclose genetic material) |
| how do viruses replicate? | viruses need a host cell to replicate that matches their receptors (they do not have capabilities to replicate on their own) |
| describe basic reproductive cycle of a virus (step 1 -2 ) | 1.Virus attaches to cell membrane. If virus has receptors specific to that cell, it moves viral proteins inside; 2.Host enzymes replicate viral genome. |
| describe basic reproductive cycle of a virus (step 3 - 4 ) | 3.Host transcribes viral genome into mRNA that makes capsid proteins using ribosomes 4.Viral genome & capsid reassemble into new viruses & exist the cell |
| describe the beginning of reproductive cycle of the bacteriophage and the paths it can take | after attaching to host cell and injecting its DNA, a phage may undergo the lysogenic or lytic cycle: |
| describe the lysogenic cycle | 1.Phage integrates with bacterial chromosome and becomes prophage in cell. 2.Bacterium reproduces normally, copying prophage to daughter cells 3. A prophage may exit the chromosome and start lytic cycle or stay dormant |
| describe dormancy of the lysogenic cycle | prophages can remain dormant for a long time until environmental (body) pressures activate it. Some viruses (ex. HIV) can mutate while replicating by making different versions of itself that the immune system doesn't recognize |
| describe the lytic cycle | 1.Like the basic virus, phage DNA & proteins are synthesized using host cell's resources and self-assemble into phages. 2. Cell lyses (bursts), releasing phages |
| explain one hypothesis for the origin of the virus | possible hypotheses: progressive (escape) hypothesis, regressive (reduction) hypothesis, virus-first hypothesis, hybrid 'chimeric' hypothesis, symbiogenic hypothesis |
| describe features of viruses that make them difficult to classify as living | viruses are only capable of characteristics of life if they have a host cell. They can move between and seek out hosts, but they are not made of cells & they do not sustain themselves much beyond replication |
| describe how viruses can cause evolution | they can complete horizontal transfer of genes across unrelated species by carrying/inserting the genome of an organism & replicating |
Created by:
AntBanana
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