BIOL 121

Question 1

Define “virus”

Answer 1

A simple, miniscule, infections, obligate intracellular parasite comprising of genetic material and surrounded by a capsid or envelope

Question 2

Why do viruses have so few genes?

Answer 2

Because they are obligate parasites and they dont need to code for complex machinery to reproduce themselves

Question 3

How large are viruses

Answer 3

usually around 20-300nm (very small)

Question 4

How large are Giant Viruses

Answer 4

around 750nm so large enough to be seen with a light microscope and have larger genomes

Question 5

What do you call transmission viruses and replication viruses

Answer 5

Extracellular virions (transmission) and intracellular virions (replication)

Question 6

How do virus populations change over time

Answer 6

they have an eclipse period of silence and then a burst of rapid growth

Question 7

How are viruses studied

Answer 7

Electron microscopy, X-ray crystallography, Cryo-EM, NMR

Question 8

what are the subunits of capsids

Answer 8

capsomers

Question 9

What is the combination of capsids and nucleic acid

Answer 9

nucleocapsid

Question 10

What shapes are viruses

Answer 10

Helical, polyhedral and Binal (complex/irregular)

Question 11

what is the function of the capsid

Answer 11

protets the nucleic acid and aids its transmission

Question 12

Do viruses need an envelope

Answer 12

No they can be enveloped and naked

Question 13

What is the structure of a bacteriophase

Answer 13

They have a head, sheath, base plate and tail fibres

Question 14

What is the replication cycle of bacteriophages

Answer 14

Adsorption, penetration, replication, maturation, release and reinfection

Question 15

What is a bacteriophage that kills its host called and what is one that isn’t

Answer 15

Lytic phages kill their hosts and temperate/lysogenic phages dont

Question 16

What is a bacteria carrying prophages called

Answer 16

lysogens

Question 17

What are phages used for

Answer 17

disinfectants and antibiotics for hard to kill bacteria as well as vaccine vectors

Question 18

How does phenogenetic analysis help in virus outbreaks

Answer 18

allows for the genome to quickly be identified by comparison to similar genetic sequence viruses

Question 19

What do all viruses have in common

Answer 19

The viral genome must make mRNA that can be read by host ribosomes

Question 20

Is mRNA +ssRNA or -ssRNA

Answer 20

always +ssRNA

Question 21

How many types of viruses are there in baltimore system and what are they

Answer 21

7 -
1 dsDNA
2 gaped dsDNA
3 ssDNA
4 dsRNA
5 +ssRNA
6 -ssRNA
7 +ssRNA with DNA intermediate

Question 22

What ways can viruses infect cells

Answer 22

1 Transformation into tumor cell via virus
2 Lysis (death of cell & release of virus
3 persistant infection (slow release without cell death)
4 latent infection (virus present but delays lysis until later triggered)

Question 23

How do viruses find cells to infect

Answer 23

They have to attatch via a receptor (excluding fungal and plant viruses)

Question 24

How do viruses enter the cell

Answer 24

1) injection of nuceic acid
2) fusion of envelope with host virus
3) Endocytosis

Question 25

What does the virus do in the cell

Answer 25

synthesises viral proteins using host ribosomes and replicating the viral genetic material

Question 26

How does the virus exit the cell

Answer 26

the virus capsid pushes against the membrane and wraps iteslf in membrane containing viral glycoproteins (produced by host ribosomes using viral genes) and naked viruses exit via lysis

Question 27

What are Viroids

Answer 27

Very small infectious agent that are NOT viruses with very small circular ssRNA, naked, resistant to proteases and only infect plants. The replication mechanism is unknown

Question 28

What are prions

Answer 28

They are small infectious proteinaceous particles (only protein no genetic material).

Question 29

How is rabies spread

Answer 29

via saliva through bites (mostly dogs)

Question 30

What are the two forms of rabies

Answer 30

Furious and dumb (furious regular form but dumb can occur and make the dog just appear sleepy)

Question 31

How is Mpox transmitted

Answer 31

Animal to human occurs via bites and scratches as well as meat from infected animals Human to human contact is via direct skin contact with lesions (only infectious after symptoms appear) and contact with contaminated fomities such as bedding

Question 32

How is Mpox treated

Answer 32

Vaccines are the main treatment (one antiviral very recently approved)

Question 33

What are obelisks

Answer 33

Viroid like elements (slightly larger) first found in human oral and stool metatranscriptomic data

Question 34

what are prion diseases called

Answer 34

spongiform encephalopathies

Question 35

How are prions caused

Answer 35

The accumulation of misfolded proteins causing other proteins to misfold as well

Question 36

What diseases are caused by prions

Answer 36

Scrapie - degenrative fatal CNS disease in sheep BSE - mad cow disease (erratic behaviour) (classical BSE can be transferred into humans causing Creutzfeld-jacob disease) Kuru - "trembling" passed on from cannibalism Creutzfeld-Jacob disease - loss of ability to think and move properly usually fatal (4 forms Sporadic, familial/inherited, Variant (meat) and Latrogenic (by accident from surgery)