Viruses Flashcards
What is a virus?
A virus is a microscopic infectious agent that requires a host cell to replicate. It consists of genetic material (either DNA or RNA) encased in a protein coat called a capsid, and sometimes an additional lipid envelope.
What are the two main categories of viral genetic material?
The two main categories are DNA and RNA. Viruses can have either DNA or RNA as their genetic material, but not both.
What are the main classes of viruses based on their genetic material?
The main classes are: 1. DNA viruses (e.g., Herpesviruses, Adenoviruses) 2. RNA viruses (e.g., Influenza viruses, Coronaviruses)
What are the key characteristics of DNA viruses?
DNA viruses have DNA as their genetic material, which can be single-stranded (ssDNA) or double-stranded (dsDNA). They often replicate in the host cell’s nucleus.
What are the key characteristics of RNA viruses?
RNA viruses have RNA as their genetic material, which can be single-stranded (ssRNA) or double-stranded (dsRNA). They generally replicate in the host cell’s cytoplasm.
What are retroviruses and how do they replicate?
Retroviruses are a subclass of RNA viruses that use reverse transcription to convert their RNA genome into DNA inside the host cell. The DNA then integrates into the host genome, where it is replicated along with the host’s DNA.
How do enveloped viruses differ from non-enveloped viruses?
Enveloped viruses have a lipid bilayer derived from the host cell membrane, which surrounds their capsid. Non-enveloped viruses lack this lipid envelope and are more resistant to environmental factors.
What is a capsid and what role does it play in a virus?
The capsid is a protein shell that encases and protects the viral genetic material. It also plays a crucial role in attaching the virus to host cells and facilitating the entry of viral genetic material into the host cell.
What are the main types of viral symmetry?
Viral symmetry can be: 1. Icosahedral - A symmetrical, spherical shape with 20 triangular faces (e.g., Adenoviruses). 2. Helical - A cylindrical shape with a helical arrangement of the capsid proteins (e.g., Tobacco mosaic virus). 3. Complex - Irregular shapes that do not fit the standard categories (e.g., Bacteriophages).
How do bacteriophages differ from animal viruses?
Bacteriophages are viruses that specifically infect bacteria. They often have complex structures and inject their genetic material into the bacterial cell. Animal viruses infect eukaryotic cells and can have a wide range of structures and mechanisms for entry and replication.
What is the lytic cycle in bacteriophage infection?
The lytic cycle is a viral replication process where the bacteriophage injects its DNA into a bacterial cell, hijacks the host’s machinery to produce new viral particles, and eventually causes the host cell to burst, releasing new viruses.
What is the lysogenic cycle in bacteriophage infection?
The lysogenic cycle involves the integration of the phage DNA into the bacterial genome, where it replicates along with the host’s DNA without immediately killing the host. This integrated phage DNA is called a prophage.
How can viral mutations affect virus behavior and pathogenicity?
Mutations in viral genomes can alter the virus’s ability to infect host cells, evade the immune system, or develop resistance to antiviral drugs. This can impact the severity of disease and the effectiveness of treatments and vaccines.
What are some common methods used to classify viruses?
Common methods include classification by genetic material (DNA or RNA), replication strategy (e.g., reverse transcription), morphology (shape and structure), and host range (type of host cells or organisms they infect).
Why is it important to study viral classifications and structures?
Understanding viral classifications and structures helps in diagnosing infections, developing vaccines and antiviral drugs, and implementing effective public health measures to control viral outbreaks.
