Ch. 6.1- General Virus Characteristics

Question 1

Define virology

Answer 1

They study of viruses

Question 2

What is the ratio of viruses to bacteria

Answer 2

10-1

Question 3

Define obligate intracellular pathogens

Answer 3

Disease causing microbes that can infect a host cell, hijack their biochemical and cellular tools to replicate.

Question 4

Define bacteriophage

Answer 4

Viruses that only infect bacteria

Question 5

Define animal viruses

Answer 5

A groups of viruses that includes viruses that infect humans.

Question 6

Define virion

Answer 6

A single infectious virus particle

Question 7

Define capsid

Answer 7

Protein shell that packages and protects the genome of a virus and makes up most of its mass.

Question 8

Define capsomeres

Answer 8

The individual three dimensional shapes that make up the capsid and determine its shape based on how they are formed.

Question 9

Define helical

Answer 9

A cylindrical type shape (trampoline spring shape)

Question 10

Define icosahedral

Answer 10

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)

Question 11

Define protein self assembly

Answer 11

When a protein does not require a chaperone to make itself into a functional three dimensional object.

Question 12

Define chaperone

Answer 12

A structure that helps proteins bend into a functional three dimensional form.

Question 13

Define naked virion

Answer 13

Virion that lack a envelope

Question 14

What are envelopes made of at least sometimes?

Answer 14

Lipid based envelope- animal viruses

Question 15

Define spikes and give another name for these.

Function?

Answer 15

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.

Question 16

What types of nucleic acid structure is used in the formation of viral genome?

Answer 16

Single and double stranded DNA and RNA. Rarely both DNA and RNA at the same time.

Question 17

Define the RNA genome function as an mRNA

Answer 17

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.

Question 18

Define: The RNA genome is complementary to mRNA

Answer 18

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

Question 19

Define: The RNA genome makes DNA that is then transcribed to make mRNA.

Answer 19

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

Question 20

Describe: The double stranded RNA genome is transcribed to make mRNA.

Answer 20

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.

Question 21

Define reassortment

Answer 21

When two different viral strains infect a single cell and their genomes are mixed and make a new viral strain.

Question 22

Define attenuated strains

Answer 22

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.

Question 23

Define tropism

Answer 23

The type of host cell or tissue a virus can infect.

Question 24

What part of the virus serves as the antigen the triggers the immune response of antibodies?

Answer 24

Spikes

Question 25

Define antigen drift

Answer 25

The mutation of the spikes of a virus that causes them to form a new kind of antigen. This is what causes our bodies to have to develop new kids of antibodies to the influenza virus every year… because antigen drift is constantly happening with the influenza virus.

Question 26

Define antigen shift

Answer 26

When major genetic reassortment occurs and the result is that the virus can infect a new host or that hosts have no residual immunity to the virus as the antigens (spikes) are so different that there has been no production of antibodies to fight off this type of viral spike.

Question 27

Define pandemic

Answer 27

A world wide outbreak of a disease that rapidly spreads and can be deadly due to the lack of immunity.