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Bio ch 19
| Question | Answer |
|---|---|
| where do viral membranes come from | host cell |
| where do viral proteins come from | the viral genome codes for them |
| role of a viral envelope | helps viruses enter host cells by binding to receptors and fusing with the membrane. |
| what determines what cells a virus infects | the surface proteins that bind to specific host receptors. |
| what does obligate intracellular parasites mean | they can replicate and reproduce only within a host cell |
| what does a host range mean? | types of cells a virus can infect |
| steps of viral replication | Infection- virus attaches/ injects DNA transcription/translation- DNA into viral proteins replication- viral DNA copied self assembly- capsids/genomes assemble release |
| lytic cycle | virus replicates, cell lyses and releases new virus |
| lysogenic cycle | viral DNA integrates into host genomes as a prophage its copied when the cell divides. |
| what are restriction enzymes | their defense mechanisms in bacteria that recognize and cut up foreign DNA |
| what's a retrovirus and how does it replicate its genome | an RNA virus that uses reverse transcriptase to convert RNA into DNA which integrates into the host genomes and makes a new virus. |
| vaccines vs antiviral | vaccines stimulate immune memory before infection- prevents infection antivirals inhibit viral replication steps, slows replication |
| horizontal transmission vs vertical transmission | horizontal- enters between individuals (between damaged cell walls in plants) vertical- offspring inheriting the virus from one parent |
| what are prions/ why their dangerous | infectious misfolded proteins, cause normal proteins to misfold leading to proteins that destroy cells and cause disease. resistant to heat and chemicals- hard to destroy they cause brain damage |
| why do new viruses emerge | mutation and host switching |
| epigenetic tags | chemical modifications (like methyl or acetyl groups) added to DNA that regulate gene expression |
| how does DNA methylation affect gene expression | silences genes (turns them off) |
| how does histone acetylation affect gene expression | loosen DNA which causes an increase in transcription (turns genes on) |
| are epigenetic changes reversible | yes they can be added or removed based on environmental signals. |
| what environmental factors affect gene expression | diet, stress, toxins, physical activity |
| what's genomic imprinting | expression of a gene depends on whether it came from the mother or father |
| how can abnormal methylation contribute to cancer | can silence tumor suppressor genes causing uncontrolled cell growth |
| why do identical twins become different overtime | environmental factors cause differences in epigenetic tags |
| what type of virus is HIV | retrovirus (RNA to DNA via reverse transcriptase) |
| what cells does HIV target | cd4+ T helper cells |
| why are viruses not considered alive | they cannot reproduce independently, they require host machinery |
| what does reverse transcriptase do | converts viral RNA into DNA |
| provirus | viral DNA integrated into host DNA |
| how does HIV use the host cell to make new viruses | host transcribes viral DNA which translates viral proteins and assembles new virions |
| how do new HIV viruses leave the cell | pinching off from the host cell membrane |
| what do viruses inject into host cells | genetic material (DNA/RNA) |
| what happens during the lytic cycle | virus replicates, cell lyses, releases viruses |
| what happens during lysogenic cycle | viral DNA integrates and remains dormant (provirus) |
| whys HIV difficult to treat | high mutation rate so is drug resistant |
| why target reverse transcriptase in HIV treatment | its unique to viruses and isn't found in host cells |
| antigenic variation | changes in viral surface proteins that help virsues evade immune system |
Created by:
Lilyhowes