Ch. 6.1- General Virus Characteristics Flashcards
Define virology
They study of viruses
What is the ratio of viruses to bacteria
10-1
Define obligate intracellular pathogens
Disease causing microbes that can infect a host cell, hijack their biochemical and cellular tools to replicate.
Define bacteriophage
Viruses that only infect bacteria
Define animal viruses
A groups of viruses that includes viruses that infect humans.
Define virion
A single infectious virus particle
Define capsid
Protein shell that packages and protects the genome of a virus and makes up most of its mass.
Define capsomeres
The individual three dimensional shapes that make up the capsid and determine its shape based on how they are formed.
Define helical
A cylindrical type shape (trampoline spring shape)
Define icosahedral
A roughly spherical shape made up of other shapes. (like a soccer ball that is made of lots of pentagon shaped patches that form a ball)
Define protein self assembly
When a protein does not require a chaperone to make itself into a functional three dimensional object.
Define chaperone
A structure that helps proteins bend into a functional three dimensional form.
Define naked virion
Virion that lack a envelope
What are envelopes made of at least sometimes?
Lipid based envelope- animal viruses
Define spikes and give another name for these.
Function?
Peplomers
Protrude from the viral capsid or from the viral envelope if one is present.
Glycoproteins help viruses attach to host cells and gain entry.
What types of nucleic acid structure is used in the formation of viral genome?
Single and double stranded DNA and RNA. Rarely both DNA and RNA at the same time.
Define the RNA genome function as an mRNA
Single stranded RNA genome directly translated by the host cell cytoplasmic ribosomes into protein.
This is called ssRNA+
I.E. polio, rubella, West Nile encephalitis, and dengue fever.
Define: The RNA genome is complementary to mRNA
Single stranded anti-sense or negative stranded have a genome that is complimentary to mRNA of the host cell.. These RNA strands have to be transcribed by virally encoded enzymes called RNA-dependent RNA polymerase (RdRPs)- these RdRPs build RNA from an existing RNA template instead of from DNA template.
All together this type of RNA translation into protein is called ssRNA-.
In short, ssRNA- has to use RdRPs to build mRNA from it’s single stranded RNA so it can be translated into protein.
I.E. influenza, ebola, rabies, measles
Define: The RNA genome makes DNA that is then transcribed to make mRNA.
Uses virally encoded enzyme reverse transcriptase to make DNA from RNA. Retroviruses do this.
DNA is inserted into the host cell genome and then the resulting mRNA is translated into proteins.
I.E. HIV, human T-cell leukemia viruses
Describe: The double stranded RNA genome is transcribed to make mRNA.
RNA is unwound so RNA polymerases can transcribe it to mRNA. RNA dependent RNA polymerases that are virally encoded are used to do this.
dsRNA
I.E. viruses that cause severe diarrhea are this type.
Define reassortment
When two different viral strains infect a single cell and their genomes are mixed and make a new viral strain.
Define attenuated strains
Mutations of viruses that make it difficult for them to infect hosts.
These don’t cause illness, but they do stimulate an immune response. Makes them ideal for making vaccinations.
Define tropism
The type of host cell or tissue a virus can infect.
What part of the virus serves as the antigen the triggers the immune response of antibodies?
Spikes
