What are the three main types of viral genomes?
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Mastering this deck will enable you to comprehend the diverse mechanisms viruses use to hijack host cells, inform antiviral strategies, and appreciate the molecular intricacies of viral life cycles—crucial for research, diagnostics, and treatment development.
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| 1 | What are the three main types of viral genomes? |
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Understand how viruses replicate at the molecular level, including viral genome types and host interactions.
Viral genomes can be DNA or RNA, and they can be single-stranded (ss) or double-stranded (ds). The main types include ssDNA, dsDNA, ssRNA, and dsRNA. |
| Think of the genome as the virus's genetic blueprint, similar to the DNA in our cells. |
| 2 | How do positive-sense ssRNA viruses replicate their genomes? | Positive-sense ssRNA viruses serve directly as mRNA upon entry; their RNA is translated into viral proteins, and the RNA-dependent RNA polymerase synthesizes a complementary negative strand that serves as a template for producing new positive-sense genomes. | Remember: positive-sense RNA acts like mRNA, ready for immediate translation. |
| 3 | What enzyme do retroviruses use to convert their RNA genome into DNA? | Retroviruses utilize reverse transcriptase to synthesize complementary DNA (cDNA) from their RNA genome, enabling integration into the host genome. | Reverse transcriptase is the enzyme that 'reverses' the usual flow of genetic information. |
| 4 | Describe the typical steps of DNA virus replication inside a host cell. | DNA viruses enter the host cell, transport their DNA to the nucleus, where they utilize host or viral DNA polymerases to replicate their genome, and transcribe viral mRNA for protein synthesis. Newly assembled virions are then released. | Think of DNA viruses as mimicking the host's own DNA replication process. |
| 5 | What is the role of viral attachment proteins? | Viral attachment proteins facilitate the specific binding of the virus to receptors on the host cell surface, determining host range and tissue tropism. | These proteins are like molecular 'keys' that unlock entry into the host cell. |
| 6 | How do enveloped viruses acquire their lipid envelope? | Enveloped viruses acquire their lipid envelope by budding through the host cell membrane or internal membranes, incorporating host lipids and viral glycoproteins into the envelope during exit. | Budding is similar to a bubble forming from a soap film—virus takes part of the host membrane with it. |
| 7 | What is the significance of the viral lifecycle stage called 'uncoating'? | Uncoating is the process of removing the viral capsid to release the viral genome into the host cell's cytoplasm or nucleus, enabling replication or transcription. | Think of uncoating as opening a sealed package to access its contents. |
| 8 | How do DNA viruses ensure their genomes are replicated within the host cell? | DNA viruses typically utilize host DNA polymerases (or their own) in the nucleus to replicate their genomes, often mimicking host DNA replication processes. | DNA viruses often hijack the cell’s own machinery for replication. |
| 9 | What distinguishes positive-sense and negative-sense ssRNA viruses in their replication strategies? | Positive-sense ssRNA viruses have genomes that function directly as mRNA, while negative-sense ssRNA viruses carry genomes complementary to mRNA and require an RNA-dependent RNA polymerase to synthesize mRNA before translation. | Positive-sense = ready to translate; Negative-sense = needs conversion first. |
| 10 | Which viral enzymes are crucial for RNA virus replication, and why? | RNA-dependent RNA polymerases are crucial because they synthesize new RNA genomes and mRNA from RNA templates, a process not performed by host cells. | Think of this enzyme as the virus's own copy machine for RNA. |
| 11 | How do some viruses evade host immune responses during replication? | Viruses encode proteins that interfere with host immune signaling, inhibit antigen presentation, or hide from immune sensors, allowing continued replication without detection. | Imagine the virus as a stealth agent avoiding detection. |
| 12 | What is the function of viral integrase in retroviral replication? | Viral integrase inserts the viral DNA, produced by reverse transcription, into the host cell genome, enabling persistent infection. | Think of integrase as a molecular 'insert' tool. |
| 13 | Explain the concept of lysogenic cycle in some viruses. | In the lysogenic cycle, the viral genome integrates into the host DNA and remains dormant (prophage or provirus) until induction triggers active replication and lytic cycle entry. | Lysogeny is like a virus going into hibernation. |
| 14 | Name a common method viruses use to exit the host cell. | Many enveloped viruses exit via budding, while non-enveloped viruses often lyse the host cell to release new virions. | Budding is like the virus taking a membrane 'cloak' as it leaves. |
| 15 | What is the significance of viral tropism? | Viral tropism refers to the preference of a virus for infecting specific cell types or tissues, dictated by receptor availability and cellular factors. | Tropism determines which tissues a virus can infect. |
| 16 | How does antiviral drug zidovudine (AZT) inhibit retroviral replication? | Zidovudine is a nucleoside analog that inhibits reverse transcriptase, preventing the synthesis of viral DNA from RNA in retroviruses like HIV. | AZT acts as a faulty building block for viral DNA synthesis. |
| 17 | What is the role of viral capsid proteins? | Capsid proteins assemble to form the protective protein shell of the virus, encapsulating the genome and facilitating attachment and entry into host cells. | Capsid is the virus's protective 'coat.' |
| 18 | Describe the process of viral assembly. | Viral assembly involves the packaging of replicated genomes and structural proteins into new virions within the host cell, often occurring in specific cellular locations depending on the virus type. | Assembly is like factory packaging of new virus particles. |
| 19 | Why do some viruses require the host cell's nucleus for replication? | DNA viruses and some RNA viruses (like influenza) depend on the nucleus for processes such as genome replication, transcription, or splicing, utilizing host nuclear machinery. | Think of the nucleus as the virus's 'command center' for certain steps. |
| 20 | What is the function of viral non-structural proteins? | Non-structural proteins assist in viral genome replication, transcription regulation, and immune evasion, but are not part of the virus particle structure. | These proteins are like the virus's internal tools. |
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