Viruses Flashcards
(25 cards)
Virion
The infective virus particle that consists of a single nucleic acid
Capsid
Protein shell of a virus composed of repeated protein subunits that packages the viral genome and delivers it into the host cell
Host range
A particular group of host species that a virus can infect
Viroids
RNA molecules that infect plants and are replicated by host RNA polymerase and have no protein capsid
Prions
Proteins that infect animals; they have no nucleic acid component
______________ viruses are polyhedral with 20 identical triangular faces and a structure that exhibits rotational symmetry
Icosahedral
Filamentous viruses
Found where the capsid consists of a long tube of protein with the genome coiled inside
T4 bacteriophages
Icosahedral “head” and helical “neck”
Poxvirusus
form of asymmetrical virus with several layers
The ICTV devised a classification system based on…
Ken elope, size of the virion, host range, capsid symmetry, and genome symmetry
What do viral lifecycles consist of…
Attachment to cells, genome entry, use host cell machinery to replicate, assemble progeny phases, exit from cell
Lytic cycle
Bacteriophage quickly replicates, killing host cells
Lysogenic cycle
Bacteriophage is quiescent; integrates into cell chromosome as a prophage
Prophage
Integration of viral genome into host genome
What enzyme helps make DNA from RNA
Reverse transcriptase
Tropism
Tissue specificity
Most animal viruses enter their hosts as ________
Virions
Uncoating
Where genome is released from its capsid
The primary factor determining the life cycle. An animal virus is the…
Form of its genome
________ uses RNA-dependent RNA–polymerase to transcript their mRNA, whereas _____________uses a reverse transcriptase to copy their genomic sequence into DNA
RNA viruses; retroviruses
Two important roles of viruses in ecosystems are….
Limiting host population density and selecting for host diversity
In the oceans, _________ are the most numerous and genetically diverse forms of life
Viruses
On a global scale, viruses play a significant role in the balance of what element….
Carbon
The decision between a bacteriophage going into either the lytic cycle or the lysogenic cycle is dictated by ____________
Environmental cues
