MCM 2-1 Virus Structure & Classification

Question 1

definition of a virus

Answer 1

an organism that encodes a capsid that is an obligate intracellular parasite associated with all life forms

Question 2

definition of a virion

Answer 2

the particle encoded by a virus genome

consists of a genome, capsid, and optional envelope

Question 3

how are viruses classified?

Answer 3

by host cell (eukaryotic/ prokaryotic, plant/insect/animal)

by viral genome type (RNA or DNA, single or double stranded)

by virion structure (enveloped or naked, helical/icosahedral, or complex

Question 4

what is the basic structure of a virus or “the viral genome must have the following three modules”

Answer 4

three basic gene modules

1. capsid proteins - structural because they form the virion. encoding molecule
2. the replicon which encodes nucleic acid polymerase, replication origin, necessary accessory proteins
3. multifactorial proteins that interact with the host. Non-structural because they are left behind in the infected cell and not packed into the virion

Question 5

unifying principles of virology

Answer 5

All viruses follow a three-part strategy for survival

1. Genome encodes a capsid that protects it outside the cell
2. Genome contains info for infecting a cell, replicating the genome, intracellular survival, and virion assembly
3. Transmission to new host is required to maintain the virus as a species

Question 6

what led to the discovery of viruses?

Answer 6

diseases led to their discovery, known as “filterable agents”

Question 7

viruses have a _____ genome

Answer 7

modular. it encodes for the capsid, replicon, and host interacting factors

Question 8

what happens to virions outside of the host cell

Answer 8

they are inert and lose infectivity over time

Question 9

virions consist of (3)

Answer 9

a few genes, encased in a protein shell, may or may not be enveloped in a membrane

Question 10

genome

Answer 10

can be DNA or RNA and can be ss, ds, circular, etc.

Question 11

nucleocapsid/capsid/core

Answer 11

protein shell that encapsulates genome

can have helical symmetry due to rolling effect of subunits

or icosahedral symmetry - 20 faces

Question 12

tegument

Answer 12

cluster of proteins outside of the nucleocapsid

Question 13

matrix

Answer 13

proteins that link the core to the envelope

Question 14

envelope

Answer 14

lipid bilayer which can surround the virion

Question 15

glycoprotein

Answer 15

glycosylated proteins found on the outside of envelope

Question 16

spike/fiber

Answer 16

glycoprotein that sticks out, important for attachment and specificity

Question 17

describe adenovirus

Answer 17

icosahedral, dsDNA, naked

DIN

Question 18

describe influenza

Answer 18

helical, dsdna, enveloped

HED

Question 19

describe herpes

Answer 19

icosahedral, dsdna, enveloped

DIE