Viruses- bio 2 exam
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43 Terms
What are viruses?
Acellular obligate parasites lacking key life characteristics like energy metabolism and independent reproduction.
What is a virion?
A single, inert virus particle with a nucleic acid genome enclosed in a protein capsid.
What are the three main hypotheses for viral origins?
Reduction hypothesis, escape hypothesis, and virus-first hypothesis.
What is the reduction hypothesis of viral evolution?
Viruses evolved from cellular organisms that became increasingly dependent on host cells.
What is the escape hypothesis of viral evolution?
Viruses evolved from genetic material that escaped from cells.
What is the virus-first hypothesis?
Viruses evolved from self-replicating molecules prior to cellular evolution.
What are the three main structural forms of viral capsids?
Helical, icosahedral, and complex.
What is a viral envelope?
A membrane surrounding the capsid with embedded viral proteins that came from the host cell.
What is the function of viral spike proteins?
To facilitate attachment to host cells by binding surface receptors.
What distinguishes +RNA from -RNA viruses?
Positive-sense RNA functions directly as mRNA, while negative-sense RNA must be copied first.
What enzyme do retroviruses use to produce DNA from RNA?
Reverse transcriptase.
What is the Baltimore system of viral classification?
Classifies viruses based on their genome type and mRNA production method.
What is viral tropism?
The specific cells and tissues a virus can infect within a host.
What are the 6 major stages of the viral infection cycle?
Attachment, entry, uncoating, replication and protein synthesis, assembly, and egress.
What are the main routes of viral entry into host cells?
Membrane fusion, endocytosis, and genome injection.
What are the primary methods of viral egress?
Cell lysis, budding, and exocytosis.
What is an oncogenic virus?
A virus that contributes to cancer
How do live attenuated vaccines work?
weakened parts of the virus are injected, creates very strong immunity but have risks
Why are viral infections difficult to treat?
Viruses replicate inside host cells, making it hard to target them without harming hosts.
What do antiviral drugs targeting replication do?
They inhibit reverse transcriptase to slow replication.
What are viruses?
Acellular obligate parasites lacking key life characteristics like energy metabolism and independent reproduction.
What is a virion?
A single, inert virus particle with a nucleic acid genome enclosed in a protein capsid.
What are the three main hypotheses for viral origins?
Reduction hypothesis, escape hypothesis, and virus-first hypothesis.
What is the reduction hypothesis of viral evolution?
Viruses evolved from cellular organisms that became increasingly dependent on host cells.
What is the escape hypothesis of viral evolution?
Viruses evolved from genetic material that escaped from cells.
What is the virus-first hypothesis?
Viruses evolved from self-replicating molecules prior to cellular evolution.
What are the three main structural forms of viral capsids?
Helical, icosahedral, and complex.
What is a viral envelope?
A membrane surrounding the capsid with embedded viral proteins that came from the host cell.
What is the function of viral spike proteins?
To facilitate attachment to host cells by binding surface receptors.
What distinguishes +RNA from -RNA viruses?
Positive-sense RNA functions directly as mRNA, while negative-sense RNA must be copied first.
What enzyme do retroviruses use to produce DNA from RNA?
Reverse transcriptase.
What is the Baltimore system of viral classification?
Classifies viruses based on their genome type and mRNA production method.
What is viral tropism?
The specific cells and tissues a virus can infect within a host.
What are the 6 major stages of the viral infection cycle?
Attachment, entry, uncoating, replication and protein synthesis, assembly, and egress.
What are the main routes of viral entry into host cells?
Membrane fusion, endocytosis, and genome injection.
What are the primary methods of viral egress?
Cell lysis, budding, and exocytosis.
What is an oncogenic virus?
A virus that contributes to cancer.
How do live attenuated vaccines work?
Weakened forms of the virus are introduced to stimulate strong, lasting immunity, though they carry potential risks.
Why are viral infections difficult to treat?
Viruses replicate inside host cells, making it hard to target them without harming hosts.
What do antiviral drugs targeting replication do?
They inhibit viral enzymes such as reverse transcriptase to slow viral replication.
What is the lytic cycle?
A viral replication pathway where the virus hijacks host machinery to replicate and ultimately lyses the host cell to release progeny virions.
What is the lysogenic cycle?
A viral replication pathway where the viral genome integrates into the host cell DNA as a prophage or provirus and replicates passively with host cell division.
What are cytopathic effects (CPE)?
Observable structural and morphological changes in host cells caused by viral infection, such as cell rounding, syncytia formation, or lysis.