Viruses general info from book

Question 1

Essential viral components

Answer 1

Protein capsid, composed of capsomers
Nucleic acid, either DNA or RNA, never both
Lipid bilayer envelope in some.

Question 2

General RNA virus characteristics

Answer 2

Most are:

Single stranded (about equal are poisitive or negative stranded) (just like RNA is usually single stranded)
Enveloped
Helical capsid
Replicate in cytoplasm

Question 3

General DNA virus characteristics.

Answer 3

Most are:

Double stranded (DNA usually is)
Icosahedral (20 sided die) symmetry
Replicate in the nucleus

Question 4

Mnemonic for the DNA virsus

Answer 4

HHAPPPY

Herpes
Hepadna
Adeno
Papova
Parvo
Pox

Question 5

DNA viruses that have envelopes

Answer 5

Herpes
Hepanda
Pox

Question 6

DNA viruses that are naked/non-enveloped

Answer 6

PAP

PAPova
Adeno
Parvo

Question 7

What RNA viruses are double stranded?

Answer 7

Reoviridae

Question 8

What RNA viruses are naked/non-enveloped

Answer 8

PCR
Picorna
Calici
Reoviridae

Question 9

What RNA viruses have icosahedral capsids

Answer 9

Reo
Picorna
Toga
FFlavi
Calici

Question 10

What RNA viruses replicate in the nucleus

Answer 10

Retro and Orthomyxo

Question 11

What are the Positive stranded RNA viruses?

Answer 11

“The CALCIfied old Emperor PICO is wearing his CROWN and RETRO TOGA and eating FLAVorful foods.

Calici
Pico
Corona
Toga
Flavi
Retroviridae

Question 12

What are the Negative stranded RNA viruses?

Answer 12

Orthologist Pete’s Rabid dog Filo fights Paul Bunyon in the Arena

Orthomyxo
Paramyxo
Rhabdo
Filo
Bunya
Arenaviridae

Question 13

What are the steps for viruses to enter a cell and reproduce?

Answer 13

1) Adsorption and Penetration
2) Uncoating
3) Synthesis and assembly of viral products
4) Release of virions from the cell (lysis, exocytosis, budding)

Question 14

How does the transcription phase differ between RNA and DNA viruses?

Answer 14

DNA viruses are more complex usually, and their transcription phase is divided into three phases instead of all at once.

DNA viral transcription
Immediate early phase
Early phase
Late phase

In the immediate and Early phase, the mRNA and proteins neccessary to replicate the bacterial DNA is transcribed,

In the late phase structural proteins for the capsid are transcribed, off of replicated DNA strands.

Question 15

Virus definition

Answer 15

A very small, non-cellular infectious agent that can only replicate inside of living, susceptible cells.

The smallest infectious agent possessing coding genes.

Question 16

Virion definition

Answer 16

A single EXTRACELLULAR, INFECTIOUS virus

Question 17

Vegetative Virus

Answer 17

An INTRACELLULAR, REPLICATIVE virus.

Question 18

What is the size range of a viruses?

Answer 18

20-300 or 400nM

Question 19

Describe viral taxonomy

Answer 19

It is based on structure and not evolution, and is thus called Artificially based.

Divided into
DNA or RNA viruses
then double stranded or single stranded
then linear or circular
RNA viruses farther divided by Positive or Negative Stranded.

Then by Capsid symmetry
Icosahedral/Cubic, Helical, or Complex
then Number of capsomers
then Diameter of the nucleocapsid

Finally,
is it enveloped or non-enveloped. (envelopes also called peplons).

Question 20

What types of nucleic acids are possible in a virus

Answer 20

RNA or DNA

Single or double stranded

Circular or Linear

Continuous or Segmented

Positive or Negative stranded for RNA.
Positive stranded is ready to code, Negative stranded requires RNA-dependent RNA polymerase to be carried in the virion.

Question 21

What are the possible characteristics of the virus capsid?

Answer 21

All are composed of capsomers. Many capsomers form an equilateral triangle to make one side of the capsid.
A single capsomer is a POLYMER of proteins and/or glycoproteins. Bound by specific, flexible, non-covalent bonds.

If the capsid and the nucleic acid is bound tightly, it is called a nucleocapsid.

Capsid shapes:
Rigid Helical, forms a rod shape
or
Flexible Helical, forms a sphere shape

Icosahedral/Cuboidal
Can also be rigid or more flexible, and then it is angular and icosahedral or more like a soccer ball.

Binal: with a helical tail and icosahedral head, seen just in bacteriophages

Complex: unique shapes like bullet shaped rhabdovirus or the brick-shaped smallpox.

Question 22

What do these suffixes mean:

viridae
virinae
virus

Answer 22

Viridae: Family
Virinae: Subfamily
Virus: genus.

Question 23

What are the ways a virus can be internalized to its host cell?

Answer 23

Non-enveloped viruses enter by internalization and endocytosis, usually by biding to a specific membrane protein on the host cell

Enveloped viruses also interact with a specific host protein, but then enter by fusion of their envelope with the host cells membrane.

Question 24

What types of viral proteins are needed for replication?

Answer 24

Polymerase,
RNA- or DNA-dependent RNA- or DNA-polymerase

Nuclease

Ligase

Question 25

What are the major types of viral proteins

Answer 25

Enzymes for replication: Polymerase, Nuclease, Ligase,

Precursor Proteins, which become Structural Protesin

Early Viral Proteins: Enzymes that repress host cell functions and redirect host cell organelles to viral replication, kinases, phosphatases

Late viral proteins: Inner and outer structural proteins of the virus

Inner structural proteins: bind viral nucleic acids
Outer structural proteins: capsid proteins that bind the virus host receptor,
Neuraminidase - cleaves sialic acid of glycoproteins to aid in cell lysis and virus release.