viruses

Question 1

why do viruses differ from all other life forms

Answer 1

no functional organelles
only replicate within a host
cannot produce their own energy
metabolically inert outside of host

Question 2

what kind of parasite are viruses

Answer 2

obligate

Question 3

replication of virus within host cell usually causes

Answer 3

cell death and eventually disease

Question 4

viruses consist of what kind of nucleic acid

Answer 4

either DNA or RNA

Question 5

what is a viruses nucleic acid surrounded by

Answer 5

a protein coat called the capsid

Question 6

some viruses have another layer around the capsid, what is it

Answer 6

the envelope, which contains membrane proteins that extend outwards

Question 7

size range of common viruses

Answer 7

20-300 nm diameter, some much larger

Question 8

3 shapes of virus capsids

Answer 8

helical (cylindrical or rod shaped), icosahedral (3D and somewhat round) and complex

Question 9

what could the viral genome be

Answer 9

dsDNA, ssDNA, dsRNA OR ssRNA

Question 10

what shape is the virus genome usually

Answer 10

single linear or circular molecule

so either RNA or DNA, ss or ds, linear or circular (except ds circular for RNA does NOT exist)

Question 11

we know some virus have a segmented genome comprised of multiple parts, what is this called

Answer 11

multi-partite

Question 12

how do viruses recognize host cell

Answer 12

surface cell receptors

Question 13

how do viruses multiply in host

Answer 13

they use host cell machinery to produce new nucleic acid and proteins, new virions are assembled and leave host cell, cell often destroyed in process

Question 14

viruses classified into groups according to:

Answer 14

type of nucleic acid
shape of capsid
envelope or not
replication strategy
genome sequence and organization
other criteria such as size, pH sensititvity, host range etc

***NOT TYPE OF DISEASE CAUSED BECAUSE VIRUSES OF SAME FAMILY CAN CAUSE RANGE OF DISEASE

Question 15

name a type of enveloped, dsDNA virus

Answer 15

herpesvirus

Question 16

name a type of non enveloped dsDNA virus

Answer 16

adenovirus

Question 17

name a type of non enveloped ssDNA virus

Answer 17

parvovirus

Question 18

name type of enveloped ssRNA virus

Answer 18

coronavirus

Question 19

name type of non enveloped dsRNA virus

Answer 19

reovirus

Question 20

name a type of non enveloped ssRNA virus

Answer 20

calicivirus

Question 21

how do you classify virus

Answer 21

family, then genus, then species (which is usually type of disease caused)
usually call them by species name

Question 22

what are viruses name after

Answer 22

usually the disease they cause but sometimes named after place they were first isolated

Question 23

should you italicize viruses

Answer 23

previously no but now YES (not widely accepted)

Question 24

why might people believe viruses existed only after evolution of first cellular life

Answer 24

because they are obligate intracellular parasites, rely on other cells

Question 25

why might believe believe viruses came before evolution of first cellular life

Answer 25

because they are simply molecular genetic parasite and could of parasitized and nucleic acid/ protein replication system including prebiotic systems (before life)

Question 26

what are issues with virus evolution

Answer 26

-no fossils
-huge diversity of viruses, do they have different ancestors?

Question 27

is it clear that some viruses do have lineages and evolutionary relationships

Answer 27

yes

Question 28

what is virus evolution theory 1

Answer 28

viruses are escaped pieces of host cell DNA (genes coding for replication enzyme and genome coating protein)

Question 29

why might virus evolution theory 1 be right

Answer 29

fits with some DNA viruses that use host-like replication processes, also fits with retrovirus which insert a DNA copy of their genome into host cell and can “pick up” host cell genes when virus replicates

Question 30

why might virus evolution theory 1 be wrong

Answer 30

emergence of a full virus genome has never been observed and genetic analysis doesn’t indicate a cellular origin for most DNA viruses

Question 31

what is virus evolution theory 2

Answer 31

-viruses are degenerate unicellular life forms (may have once be small cells that parasitized larger cells and over time genes that were not required were lost)

Question 32

why might virus evolution theory 2 be right

Answer 32

fits with large DNA viruses which psychically resemble bacteria and have complex genomes

Question 33

why might virus evolution theory 2 be wrong

Answer 33

sequence of viral genomes indicates that they did not originate from bacterial or other unicellular genomes, instead they have distinct viral lineages

Question 34

what is virus evolution theory 3

Answer 34

viruses originated independently from host cells, with several separate viral origins occurring at different times

RNA virus may have origins in the RNA world
DNA viruses likely co evolved w their hosts while the DNA world was developing

Question 35

which virus evolution theory has most supporting evidence

Answer 35

3

Question 36

how are many of major viral diseases controlled

Answer 36

vaccination programs

Question 37

are viruses the top of the list as the cause of emerging diseases

Answer 37

yes, because, mutations expand host range and increase virulence
as well disruption to ecosystems and social factors bring animal species closer together

Question 38

provide an example of different types of viruses of veterinary significance

Answer 38

henipavirus: hendra and nipah viruses
both viruses maintained in flying fox fruit bats
trasnmit to humans via horses (hendra) or pigs (nipah) or directly from bats