Podcast Beta
Questions and Answers
What is the primary purpose of virus replication?
In which stage of the virus replication cycle does the capsid break down?
Which of the following statements about virus assembly is correct?
What role do co-receptors play in the virus attachment process?
Signup and view all the answers
Which of the following stages is NOT required by all viruses in the replication cycle?
Signup and view all the answers
What determines the tropism of a virus?
Signup and view all the answers
Which method is used by enveloped viruses to enter host cells?
Signup and view all the answers
Why are transgenic mice expressing CD155 important for studying poliovirus?
Signup and view all the answers
What is a key characteristic of viruses that can undergo cell-cell membrane fusion?
Signup and view all the answers
What hinders the effectiveness of vaccines against certain viruses like HIV?
Signup and view all the answers
What is the primary function of uncoating in the virus replication cycle?
Signup and view all the answers
Which type of viruses must transport their genomes into the nucleus?
Signup and view all the answers
Which genome type typically requires RNA polymerases for gene transcription?
Signup and view all the answers
Which of the following viral genomes does NOT require entry into the nucleus for replication?
Signup and view all the answers
What replication strategy does the viral genome follow?
Signup and view all the answers
What distinguishes dsRNA viruses from RNA viruses that reverse transcribe?
Signup and view all the answers
Which of the following statements is true regarding parvoviruses?
Signup and view all the answers
What type of genomes can viral genomes possess?
Signup and view all the answers
How do RNA viruses cope with monocistronic mRNA limitations?
Signup and view all the answers
What is the primary function of an internal ribosome entry site (IRES) in RNA viruses?
Signup and view all the answers
Why are RNA viruses more prone to mutations compared to DNA viruses?
Signup and view all the answers
What is the role of scaffolding proteins during the assembly of RNA viruses?
Signup and view all the answers
Which of the following statements correctly describes the packaging signal in RNA viruses?
Signup and view all the answers
During which stage of the viral replication cycle does the maturation of the virus occur?
Signup and view all the answers
What distinguishes the mutation rates of RNA viruses from those of DNA viruses?
Signup and view all the answers
What is the role of reverse transcriptase in retroviruses?
Signup and view all the answers
What is the role of the viral protease in the maturation of HIV?
Signup and view all the answers
What is the primary process by which enveloped viruses escape from an infected cell?
Signup and view all the answers
In the context of virus replication, what does the term 'eclipse period' refer to?
Signup and view all the answers
What is the burst size in a virus growth curve?
Signup and view all the answers
Which characteristic is typically true regarding defective viral particles?
Signup and view all the answers
How does lysis of a cell differ from budding in the context of viral release?
Signup and view all the answers
What does the multiplicity of infection (MOI) indicate?
Signup and view all the answers
Which factor is essential for the curving of membranes in enveloped virus release?
Signup and view all the answers
Study Notes
Virus Infection and Replication
- Virus must replicate to create new virions for continued infection.
- Replication involves breaking down the virion capsid, releasing the genome, and assembling new particles.
- Virions assemble de novo, unlike the process in cell division.
Virus Replication Cycle
- Involves seven stages: attachment, penetration, uncoating, replication, assembly, maturation (some viruses), and release.
- These stages may not occur in a strict order.
Attachment
- Involves viral binding to host cell at the plasma membrane through specific receptors.
- Some viruses, like HIV, require co-receptors for effective binding.
- Virus attachment specificity influences the tropism (host range) of the virus.
- Example: Poliovirus requires CD155 for infection; transgenic mice expressing CD155 can be infected.
Penetration
- The virus crosses the plasma membrane using various methods.
- Enveloped viruses typically enter through membrane fusion; some also employ cell-to-cell transmission.
- Vaccine challenges arise as viruses can evade antibodies when hidden inside cells.
Uncoating
- Release of the viral genome via capsid breakdown occurs through various mechanisms.
- Some viruses transport their genomes into the nucleus, often at the nuclear envelope.
Replication
- Viral genome replication varies by nucleic acid type (DNA or RNA).
- Genome categorization: dsDNA, ssDNA, dsRNA, +ssRNA, -ssRNA, and retroviruses.
- DNA viruses usually enter the nucleus to utilize host machinery, except poxviruses, which replicate in the cytoplasm.
- RNA viruses utilize strategies like polyproteins and Internal Ribosome Entry Sites (IRES) for protein synthesis.
- RNA viruses have higher mutation rates than DNA viruses due to the lack of proofreading capability in RNA-dependent RNA polymerases.
Assembly and Maturation
- Assembly involves the formation of a mature virion around scaffolding proteins and viral DNA.
- Maturation includes proteolytic cleavage of viral proteins, necessary for virion infectiousness.
- Example: HIV Gag polyprotein is cleaved post-release to form an infectious particle.
Release
- Nascent virions escape the infected cell, typically through budding for enveloped viruses.
- Budding involves viral protein interactions with cellular membranes, forming the viral envelope.
- Non-enveloped viruses generally exit via cell lysis.
Virus Growth Curves
- One-step growth curves track the replication cycle parameters.
- Multiplicity of Infection (MOI) defines the number of viral particles per cell.
- Key phases include the eclipse period (no released particles) and latent period (time with no infectious release).
- Burst size indicates the total number of virions released from each cell.
Defective Viral Particles
- The ratio of non-infectious to infectious particles is typically higher than 10, indicating many released particles are non-infectious (defective).
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on the stages of virus infection and replication. This quiz covers the key processes involved, including attachment, penetration, and the overall replication cycle of viruses. Understand how viruses interact with host cells and the implications of these interactions.