Medical Micro - virus

Question 1

what percentage of viral proteins form the capsid

Answer 1

50-90%

Question 2

how does viral genome size vary

Answer 2

4-2500 coding genes

Question 3

what are viroids

Answer 3

circular ssRNA
no protein capsid
no protein-coding gene
mostly present in plant pathogens

Question 4

outline regressive theory of viral origin

Answer 4

free-living organisms became parisitic
over time they lost alot of their function - explains small genome size

Question 5

what are the disadvantages of the regressive theory

Answer 5

there is too large a gap between a virus and the simplest of parasites

Question 6

outline the escape theory of viral origin

Answer 6

genetic material that escaped from larger organisms
there are other examples of this like transposons

Question 7

what is the main drawback of the escape theory to viral origin

Answer 7

doesn’t explain viral structure

Question 8

outline the ancient theory of viral origin

Answer 8

self-replicating molecules from pre-cellular world
explains fundamental difference between virus and other life

Question 9

what is the drawback to the ancient theory of viral origin

Answer 9

unexplained how virus-ancestors replicated without a host

Question 10

how are viruses classified

Answer 10

based on structural traits:
capsid
nucleic acid type
absence/presence of envelope

Question 11

what are the 7 classifications of life and which do viruses check

Answer 11

organisation -/
metabolism
response to stimuli
homeostasis
growth
reproduction -/
evolution -/

Question 12

what are the 5 steps of viral replication

Answer 12

attachment
penetration
nucleic acid and protein synthesis
assembly and packaging
release - lysis

Question 13

outline the basics of how HIV binds to CD4

Answer 13

binds to CCR5/CXCR4
still too far, requires co-factors to fuse membranes

Question 14

what is the difference between how non-enveloped/enveloped animal viruses penetrate

Answer 14

non-enveloped - enters via endocytosis
enveloped - enters via fusion, needs uncoating of nucleocapsid to release nucleic acids

Question 15

how do viruses enter plant cells

Answer 15

cell wall makes it harder so they find damaged cell walls to enter
or they use a vector

Question 16

how do virus inject their material into a bacterial cell

Answer 16

bacterial cell wall is too rigid to cross
so the virus binds to the surface
the tail sheath contracts and the tail core is pushed through the cell wall and the genetic material is injected into the cytoplasm
sound familiar?

Question 17

what is the difference between DNA virus and RNA virus synthesis

Answer 17

DNA - can be synthesised by host cell machinery
RNA - need to synthesis it themselves
because RNA-dependent RNA polymerase is absent in the host

Question 18

what can genomic RNA act as in some RNA-viruses

Answer 18

functions as mRNA

Question 19

outline the process of budding

Answer 19

virus is within an endosome
nucleic acid and capsid separate
nucleic acid encodes for envelope proteins
nucleic acid returns to capsid
envelope proteins join at the exosome
progeny virus is released from the cell

Question 20

difference between vertical and horizontal gene transfer

Answer 20

vertical - transfer of genetic material from parent to offspring
horizontal - transfer from one lineage to another

Question 21

features of mimivirus/mamavirus/megaviruses

Answer 21

large viruses infecting amoebae
400-800nm
~1000 protein coding genes

Question 22

how large is an E. coli approx.

Answer 22

~ 2μm x 500nm

Question 23

features of sputnik viruses

Answer 23

small virus infecting amoebae
virophage

Question 24

when can sputnik viruses infect amoebae

Answer 24

cannot infect amoebae on its own
can only infect it if its already infected by a mimi/mamavirus

Question 25

features of pandavirus

Answer 25

largest virus genome - 2x the size of a megavirus
~ 2500 protein-coding genes
infects amoebae

Question 26

features of pithovirus

Answer 26

found in siberian permafrost
1.5μm x 500nm
infects amoebae

Question 27

features of medusavirus

Answer 27

infects amoebae
forces host to form a thick hardened shell
what could this be?

Question 28

features of polydnavirus

Answer 28

it is an insect virus found in parisitoid wasps
incorporated in wasp genome
only reproduces using wasp’s reproductive system
injected via eggs and enter host blood cells
reduces immune response