Are virophages a type of virus or something different?
It must have a capsid and a nucleic acid, which can be double-stranded or single-stranded, circular or linear, and DNA or RNA. Virophages are therefore a type of virus.
Virophages only
- always smaller than Bacteria and Archaea
- they lack the genes for proteins needed to replicate themselves
Non-virophage viruses only
the genetic information can be in the form of DNA or RNA
Both virophages and other viruses
- can’t replicate on their own
- don’t belong to the 3 domains
- have a protein capsid surrounding their nucleic acid
Neither virophages nor other viruses
- generate energy through mitochondria
- use their own ribosomes to make proteins
Double stranded DNA
- DSD viruses have processes of replication, transcription, and translation that are the most similar to those used by cells
- is the genetic material of virophages
Retro viruses
contain an RNA-dependent DNA polymerase called reverse transcriptase that is used generate a DNA intermediate
Single stranded RNA and double stranded DNA viruses
carry their own nucleic acid polymerases (replicases) to replicate the viral genome with no DNA intermediate
Single stranded DNA viruses
have replication that involves first generating a complementary DNA strand
Single stranded DNA and double stranded DNA viruses
replicate using DNA polymerases, either their own or from those of the host
What is another way that cells have evolved to avoid viral infection?
An attachment receptor on the host cell surface that is recognized by the virus is mutated.
Virophages interfere with the life cycle of megaviruses by competing with them for replication enzymes, causing defective megaviruses to be produced. When the life cycle occurs correctly, what are the steps?
- virus attaches to host cell which are mediated by cell surface receptors
- penetration of nucleic acids into host cell and the capsid is discarded
- host cell enzymes and replication machinery are used to synthesize new viral genetic and capsid material
-newly synthesized viral genomes and capsids are assembled into complete viral particles - the host cell lyses releasing the newly assembled virus particles
The cycle of megaviruses differs from those of bacteria and animals. During which part of the bacteriophage life cycle will the viral genome be replicated in synchrony with the host cell?
lysogenic
What structure can the viral genome take?
ss-DNA
ds-DNA
ds-RNA
Why does the structure of plant and bacterial cells illustrate the reason for having few enveloped viruses that infect these cells?
Plant and bacterial cells contain cell walls that limit the virus from budding out and obtaining the envelope.
Steps in the bacteriophage replication cycle
- attachment
- penetration of the viral nucleic acid
- synthesis of viral nucleic acid and proteins
- assembly and packaging of new viruses
- cell lysis and release of new virions
What component(s) make up the structure of a virion?
capsid and genome
Some viruses have plus sense RNA genomes. Which of the following could describe one of those viruses?
a virus that contains RNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products
