Viruses And Subviral Agents Flashcards
Contrast a virus with a cellular organism.
Viruses contain the nucleic acids necessary to make copies of themselves, but in order to reproduce they must invade living cells and commandeer their metabolic machinery
What is a virus?
It is a very small infective agent that consists of a core of nucleic acid and is dependent on a living host
Describe the structure of a virus.
A virus is a subcellular particle consisting of a DNA or RNA genome surrounded by a protein coat or outer envelope
Identify characteristics used to classify viruses
Viruses are classifies based on host range, size, shape, presence of an envelope, and method of transmission from host to host
What is the host range?
It is the base for viruses to be classified by: the type of organisms they infect, the type of nucleic acid they contain, and whether the nucleic acid is single-stranded or double-stranded
What are bacteriophages?
Also known as phages; they are complex viruses that infect bacteria. They typically consist of a long molecule of dsDNA coiled within a polyhedral head
Contrast a lytic and lysogenic cycle.
In a lyric cycle, the virus destroys the host cell. In a lysogenic cycle, the genome of a temperate virus can be replicated along with replication of the host’s DNA without causing death of the host cell.
What are the five steps in a lytic cycle?
- Attachment to the host cell
- Penetration of viral nucleic acid into the host cell
- Replication of the viral nucleic acid
- Assembly of newly synthesized components into new viruses
- Release from the host cell
What is a prophage?
The nucleic acid of some phages that was integrated into the bacterial DNA
What happens in lysogenic conversion?
Bacterial cells containing certain temperate viruses exhibit new properties
Describe the virus infections of plants.
Most plant viruses are ssRNA viruses that do not have envelopes. Plant viruses can be spread among plants by insect vectors via plasmodesmata
Describe the viral infection of animals.
Viruses enter animal cells by membrane fusion or endocytosis. Vital nucleic acid is replicated within the host cell, proteins are synthesized, and new viruses assemble and release from the cell
Describe the reproductive cycle of a retrovirus.
They use reverse transcriptase to transcribe their RNA genome into a DNA intermediate that becomes integrated into the host DNA. Copies of the viral RNA are then synthesized.
Compare and contrast satellites, viroids, and prions.
Satellites reproduce only with the help of a helper virus. A viroid consists of a short strand of RNA with no protein coat. A prion consists only of protein.
