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Tobacco mosaic virus
The first virus discovered, identified by D. M. Iwanowsky as a 'filterable virus' smaller than bacteria.
Virion
A complete virus particle, consisting of the viral genome and the protein coat.
Capsid
The protein coat of a virus that protects the nucleic acids.
Bacteriophage
A type of virus that infects bacteria.
Lytic cycle
The viral reproduction cycle in which the host cell is destroyed to release new virions.
Lysogenic cycle
A viral reproductive cycle in which the virus integrates its DNA into the host's genome. Will wait for an appropriate signal to activate and enter the lytic cycle, leading to the production of new viral particles.
Filamentous phages
A type of phage that looks like long fibers and causes productive infections without killing host cells.
Generalized transduction
A process where bacterial DNA is accidentally packaged into a phage and transferred to another bacterium.
Specialized transduction
A process where a temperate phage transfer bacterial genes during its transition from lysogenic to lytic cycle.
Viroids
Small, circular RNA molecules that infect plants and can cause various diseases.
Prions
Infectious agents composed solely of protein, linked to neurodegenerative diseases.
CRISPR
A bacterial defense mechanism against phage infections involving RNA-guided cutting of viral DNA.
Capsomeres
The individual protein subunits that make up the capsid of a virus.
Obligate intracellular parasites
Organisms, like viruses, that can only replicate within a host cell.
Nucleocapsid
The combination of a virus's nucleic acid and its protective capsid.
Prophage
The viral DNA that is integrated into the bacterial host's genome during lysogenic infection.
Antigenic drift
The gradual accumulation of mutations in the genes that code for virus surface proteins.
Eicosahedral
One of the three general shapes of viruses, resembling a spherical shape with triangular faces.
Helical
One of the virus shapes characterized by a spiral structure.
Complex viruses
Viruses with complex structures, often made up of both icosahedral and helical features.
Matrix protein
Protein found between the nucleocapsid and the viral envelope.
Oncoviruses
Viruses that can cause cancer in humans.
Latent infection
A state where the virus is present in the body but not actively replicating.
Budding
The process through which enveloped viruses exit the host cell, acquiring an envelope.
Enteric viruses
Viruses that are transmitted through the oral-fecal route.
Zoonotic viruses
Viruses that are transmitted from animals to humans.
Reverse transcriptase
An enzyme that synthesizes DNA from an RNA template, characteristic of retroviruses.
Restriction-modification system
A bacterial defense mechanism involving restriction enzymes that cut foreign DNA.
Viral oncogenes
Viral genes that can induce tumor formation in host cells.
Viral genome
The complete genetic material of a virus, which can be either DNA or RNA.
Thermal stability of prions
Prions are resistant to heat and chemical treatments, making them difficult to destroy.
Protease resistance
Characteristic of prion proteins, making them resistant to degradation.
Lysogenic conversion
A process through which the phenotype of a bacterial cell changes due to the presence of a prophage.
Acute infection
An infection that has a rapid onset and short duration.
Persistent infection
An infection that lasts for years or a lifetime, with possible recurrent symptoms.
Define virus replication.
The process by which a virus makes copies of itself within a host cell.
What are the two main types of virus replication cycles?
Lytic cycle and lysogenic cycle.
What is the role of attachment proteins?
This facilitates the binding of viruses to specific host cell receptors.
What is a temperate phage's key characteristic?
It can enter a lysogenic phase, integrating its DNA into a host genome.
What triggers phage induction?
Environmental stresses can trigger a switch from lysogenic to lytic cycle, leading to phage induction.
What is the significance of viral envelopes?
Helping in the entry and exit of viruses from host cells and also play a role in immune evasion.
How does RNA genome structure differ among viruses?
ss(+) RNA serves directly as mRNA, ss(-) RNA must be transcribed, and ds RNA is segmented and needs uncoating.
What are common characteristics of enveloped viruses?
Enveloped viruses generally have a lipid membrane, spikes for attachment, and are typically more fragile than naked viruses.
What is the function of the matrix protein in viruses?
The matrix protein provides structural support and is involved in the assembly and release of viral particles.
naked vs enveloped
Naked viruses often induce a stronger immune response due to their stable structure, while enveloped viruses may evade detection.
What can trigger a latent infection to become active?
Various stressors, such as hormonal changes or immunosuppression, can reactivate latent infections.
What are some diseases caused by oncoviruses?
Oncoviruses can be linked to cancers such as cervical cancer and certain types of leukemia.
What role do restriction enzymes play in bacteria?
They cut foreign DNA, providing a defense against viral infections.
Generalized transduction
A method of gene transfer in bacteria where any bacterial DNA is packaged into a phage during viral assembly.
Specialized transduction
A method of gene transfer in bacteria where specific bacterial genes are transferred by a temperate phage during the transition between lysogenic and lytic cycles.
Key difference between generalized and specialized transduction
Generalized transduction can transfer any genes, while specialized transduction only transfers specific genes associated with the prophage.
ss(+) RNA viruses
These viruses can serve directly as mRNA and are translated by host ribosomes to produce viral proteins.
ss(-) RNA viruses
These viruses must first be transcribed into complementary ss(+) RNA before they can be translated into proteins.
ds RNA viruses
These viruses have double-stranded RNA genomes that are often segmented; they must be uncoated to release the individual segments for transcription.
DNA viruses
These viruses utilize the host's cellular machinery to replicate their DNA and produce viral proteins often in the nucleus.
reverse transcribing viruses
These viruses, such as retroviruses, use reverse transcriptase to convert their RNA genome into DNA after entering the host cell.
