Lec 10-Intro

Question 1

What are viruses?

Answer 1

Simple machines that have evolved to replicate in certain hosts, very small with big impact. Submicroscopic, obligate intracellular parasites

Question 2

What is the relation of virus, disease, and infection?

Answer 2

Infection with a virus does not always result in disease—disease is more rare

Question 3

How can studying viruses help us?

Answer 3

Disease prevention, helps us understand aspects of host bio

Question 4

Where are viruses?

Answer 4

Everywhere, we eat and breathe them regularly and carry viral genomes. They infect pets, wildlife, plants, etc. and can cross species barriers (i.e. zoonotic infections)

Question 5

How many virus particles per 1mL seawater?

Answer 5

10 million

Question 6

What are marine viruses?

Answer 6

• Impact global carbon cycle
• Viruses represent a large amount of biomass in the ocean, 10^30 viruses in oceans
• Affects marine animals

Question 7

Calcivirus:

Answer 7

• Whales commonly affected by it
• Causes rashes, blisters, diarrhea
• Infected whales shed 10^13 viruses per day

Question 8

List 3 whale viruses and symptoms

Answer 8

1. Calcivirus: rashes, blisters, diarrhea
2. Paramyxoviruses: measles
3. Orthomyxoviruses: influenza

Question 9

How infected are we with herpesvirus?

Answer 9

Everyone has at least 2 of 8 herpes viruses which all have persistent, lifelong infections

Question 10

3 examples of herpes viruses

Answer 10

1. VZV—chickenpox/shingles
2. HCMV—cytomegalovirus (flu/chickenpox symptoms)
3. EBV—mono, MS precursor

Question 11

Human virome (tissues)

Answer 11

Diff tissues have diff associated viruses

Question 12

Ancient viral infections

Answer 12

Presence of viruses is evident in genomes of vertebrates, allowing us to trace back

Question 13

What are retroviruses?

Answer 13

• Integrate into host genomes i.e. HIV
• 10% of human genome has retrovirus sequences
• Similar findings in other animals genomes

Question 14

Heritability of viral sequences: infection of germ-line cells

Answer 14

If a retrovirus infects skin cells, it won’t pass to future generations—has to be in germ-line cells to be passed to progeny

Question 15

Example of germ-line cells in koalas?

Answer 15

Infectious cause of KIDS (koala immune deficiency syndrome) is integrated into genome and passed to progeny. Can be spread horizontally (same gen) and vertically (future gens)

Question 16

Integrated ancient viruses: syncytin

Answer 16

• Syncytin is a viral gene belonging to endogenous retrovirus
• Involved in cell attachment and located on chromosome 7
• Essential for placental development: fuses cells into a multinucleate cell, and creates placenta (semipermeable barrier between mother and fetus)
• Any animal with placenta has synctin gene

Question 17

What did integrated ancient viruses do

Answer 17

Influenced human evolution eg. Syncytin

Question 18

Integrated ancient viruses: KHSV

Answer 18

KSHV is a herpes virus. Genes are captured from primate ancestors

Question 19

What’s the point of syncytin and KSHV examples?

Answer 19

Viruses can deliver and capture genes from hosts, and viruses can co-evolve with their hosts

Question 20

How are virus particles produced?

Answer 20

• Assembly of pre-formed components
• In comparison, bacteria double in size and contents, then divide—in contrast, viruses make their components in hosts and then assemble like lego

Question 21

Do viruses grow or divide?

Answer 21

No

Question 22

Virus access to mitochondria:

Answer 22

Viruses cant generate their own metabolic energy i.e. ATP and cant synthesize proteins because it would use too much energy. Viruses can access ribosomes/proteins from host but dont have their own protein synth machinery

Question 23

Do viruses replicate? Where?

Answer 23

Yes, in and out of cells

Question 24

Does survival of the fittest apply to viruses?

Answer 24

Yes

Question 25

Are viruses alive?

Answer 25

Not sure—one view is inside host they are and outside hosts they aren’t. Instead of growing, they just multiply by using cell processes to direct genome replication

Question 26

Shape and size of viruses:

Answer 26

Variety—but most are smaller than bacteria. Many viruses need to be seen under EM

Question 27

Visualizing viruses with indirect method

Answer 27

Plaque assays:
-If you have a virus that destroys the host cell as part of its replication cycle, we can count them
1. Infect host cells with inoculum
2. Add them to susceptible cells
3. Overlay with agar—the only way other cells will be infected is lateral spread
4. Wait for cytopathic effect (cell destruction). Dying cells have holes (plaques) in the center

Question 28

Visualizing viruses with direct method

Answer 28

TEM