Section 4 Final Exam

Question 1

Giant viruses are called:

Answer 1

Nucelocytoplasmic large DNA viruses (NCLDVs)

Question 2

NCLDVs facts

Answer 2

• 6 families
• large ds DNA geomes
• share sets of “core” genes

Question 3

Phycodnaviruses have been found in ______ and show decline in performance on cognitive tests

Answer 3

brain

Question 4

Mice that were infected with virus containing algae showed: (3 things)

Answer 4

1- decline in cognitive test performance
2- 1/3 had antibodies against the virus
3- showed changes in genes associated with cognitive function and immunity

Question 5

algae that have chalk plates on the outside of their cells: __________

viruses that infect this chalk type of algae: _____________

Answer 5

coccolithophores

cocolithoviruses

Question 6

coccolithophores form:

Answer 6

large blooms in ocean seen from space due to their chalky exterior
when blooms end, lots of cocolithoviruses are found in seawater

Question 7

cocolithoviruses (ex. EhV-86) encode

Answer 7

proteins that synthesize the sphingolipid ceramide

Question 8

sphingolipid ceramide from cocolithoviruses are involved in: (2 things)

Answer 8

1- forming lipid rafts in cells membrane to allow virus to exit
2- blocking the cells apoptosis pathway to allow the virus to keep replicating

Question 9

effect of cocolithovirsues on climate

Answer 9

1- Lysis of these algeal cells releases volatile chemical DMS (dimethyl sulfide) that forms clouds
2- these clouds prevent sunlight to ocean and block phytoplankton growth
NEGATIVE FEEDBACK

3- white cliffs or Dovers made from liths come out

Question 10

NCLDVs #2:

Answer 10

mimiviruses

mimi= mimicking microbe

Question 11

mimiviruses infect:

Answer 11

amoeba cells

Question 12

mimivirus strucrure

Answer 12

• star shaped at one vertex “stargate”
• multiple membrane layers
• long protein/sugar fibers that make it resemble bacteria

Question 13

Under the stargate shaped there is ____ _________ and intead, it is filled with proteins that are involved in the first stages of infection

Answer 13

no DNA

Question 14

once star-shaped vertex opens:

Answer 14

viral membrane and phagosome membrane fuse and DNA is released into cytoplasm

Question 15

mimivirus replication and assembly happens in ______ _______ in the host cells cytoplasm and NOT in the nucleus like usual

Answer 15

viral factory

Question 16

viruses released from edges of _____ _______

Answer 16

viral factory

Question 17

how are viruses made in viral factories

Answer 17

DNA packaged into particles at the outside edge of the factory and it exits through a portal on the opposite end of the stargate opening
- capsids filled with DNA at outer edge of viral factories

Question 18

speculated that mimiviruses can cause ___________

Answer 18

pnemonia

Question 19

proposed that girus evolution traces back to __________ and the family tecivididae based on the presence of some conserved genes in tectiviruses polintons transposons virophages plasmids viruses and other viruses

Answer 19

bacteriophages

Question 20

Where did giruses come from?

Answer 20

1- bacterium infected by tectivirus was a endosymbiont that became mitochondria
2- tectivirus became a “polinton” (type of transposon) that was encoded in the nucleus
3- polinton escaped the nucleus and gained some cellular genes
4- the escaped version swapped genes and became the progenitor of mega viruses
5- polintons evolved more and became virophages adenoviruses bidnaviruses etc

Question 21

Mimiviruses genome

Answer 21

• larger than many bacterial genomes
• many genes that were never found in viral genomes (cellular genes)
• some translation genes but not enough to do it on its own
• gene got so big due to duplications on the ends of the genome
• many orphans (genes not found elsewhere

Question 22

many of girus genomes contain different _____ _____ ______ within them

Answer 22

mobile genetic elements (MGE)

Question 23

proposed that MEGs are symbionts within the viral genome as they assist the virus in _____-______ ______ when there is many viruses trying to infect the same cell

Answer 23

virus-virus competition

(MEG makes virus win, virus wins, and MEG gets more distributed SYMBIOSIS)

Question 24

Two types of MGE

Answer 24

1- restriction/modificatiom systems: degrade other viral DNA and host DNA and use it for their viruses replication
2-Homing endonuclease introns: splice out from genome and into the competing virus inactivating its genes/proteins