Viruses

Question 1

Obligate Parasites

Answer 1

Viruses are NOT living creatures until they have attached to and invaded a living organism

Question 2

DNA viruses

Answer 2

Hepatitis B
Herpes Simplex 1 (cold sores)
Herpes Simplex 2 (genital herpes)
Herpes Simplex 3 (Varicella Chicken Pox & Zoster Shingles)
Herpes Simplex 4 Infectious Mononucleosis (Epstein-Barr Virus)
HPV (genital warts)
Smallpox (Variola)

Question 3

RNA Viruses

Answer 3

Influenza
Red Measles (Rubeola)
Pneuomonitis/Bronchiolitis (Respiratory Syncytial Virus RSV)
HIV and AIDS
Norovirus
Polio
German Measles (Rubella)
Hepatitis A and C
West Nile Virus
COVID19 (SARS)

Question 4

Approximate size of viruses

Answer 4

Extremely tiny, within the realm of nanometers (bacteria are within the realm of micrometers)

Question 5

How do viruses attach?

Answer 5

Viruses are host-specific and attach to receptor sites
1. Enveloped viruses take a bit of the host’s membrane system with them and are pleomorphic since the envelope is more supple than the capsid (glycoprotein spikes for attachment)
2. Non-enveloped viruses have only the capsid layer protecting the genetic material (capsid molecules for binding and attachment)

Question 6

Types of Virus Morphology

Answer 6

-Helical
-Polyhedral
-Enveloped & Spherical
-Complex

Question 7

Methods of Culturing Viruses

Answer 7

-Viral Plaque Method
-Animals and Transgenic animals
-Tissue Culture Method
-Cytopathic Effects
-Embryonated Eggs

Question 8

Culturing

Viral Plaque Method

Answer 8

Growing a virus over a layer of bacteria on a plate (plaques are the holes in the bacterial layer which indicated areas of host cell death aka zone of lysis by virus)

Question 9

Culturing

Tissue Culture Method

Answer 9

grow tissue cultures and put viral cells on them, watch them go

Question 10

Culturing

Cytopathic Effects

Answer 10

unleash virus on host tissue and look for cytopathic effects (patterns) (can be used on chick and rat embryo cells)

Question 11

Culturing

Embryonated Eggs

Answer 11

embryonated eggs have a variety of areas doe viruses to targets, eggs are innoculated with virus and are cultivated MOST COMMON METHOD USED TODAY since eggs are cheap and readily available

Question 12

Methods of diagnosing virus

Answer 12

-Electron microscopy (to look at size, structure, and number & arrangement of capsomeres)
-CPEs, inclusion bodies in host tissue
-Serology
-Nucleic acid probes

Question 13

T-Even Phages

Answer 13

-Important structures include the Polyhedral Capsid Head, DNA (genetic information), Helical Tail, Tail Sheath, Pin & Plate, and Tail Fibers
-Not enveloped and only attach to bacteria
-Best understood and most studied virus

Question 14

T-4 Virus

Answer 14

Virus that typically parasitizes E. coli organisms

Question 15

Life Cycle of Bacteriophage

Answer 15

1. Attachment
2. Penetration/Entry
3. Biosynthesis
4. Assembly/Maturation
5. Release

Question 16

Attachment

Answer 16

Tail fibers attach to host receptor proteins (very specific because of this) via random collision

Question 17

Penetration/Entry

Answer 17

Bacteriophage injects hydrolytic enzyme into host cell by contracting tail sheath and forcing the internal hollow tube within the tail through the host’s cell wall and membrane (like a hypodermic syringe)
*Bacteriophages for animal viruses enter via endocytosis, fusion, or direct penetration (non-enveloped bacteriophages)

Question 18

Biosynthesis

Answer 18

After entry, enzymes degrade the bacterial DNA and Bacterium stops synthesizing its own molecules and begins synthesizing new viruses under the direction of the viral genome

Question 19

Assembly/Maturation

Answer 19

Not entirely understood
Parts of the bacteriophage accumulate within the cell and spontaneously attach to each other to form new virions

Question 20

Transduction

Answer 20

Transfer of DNA from old host to new host when the viral capsid assembles around pieces of host DNA

Question 21

Release (bacteriophage life cycle)

Answer 21

Viruses are released from the host bacterial cell as the lysozome completes its degradation of the host’s wall and the bacterium lyses
-Non-enveloped: released from animal cells through exocytosis, which may cause lysis and death of the cell
-Enveloped: often released through budding or exocytosis. Virus exits cell with envelope derived from a plasma or organelle membrane. Host cells die eventually due to all the damage from the viral occupants

Question 22

Eclipse Period

Answer 22

the time period from attachment to pre-assembly where virions penetrate host’s cells. (time between successful cell infection and start of virus production)

Question 23

Burst Time

Answer 23

the time period from attachment to release (lysis). The number of virions released per infected bacterium

Question 24

Latency

Answer 24

when animal viruses remain dormant in host cells. In asymptomatic host, viruses are not usually released unless activated (Herpes Simplex, Chicken Pox/Shingles)

Question 25

Temperate Virus

Answer 25

viruses continuously released (Hepatitis B, HPV, HIV)

Question 26

Virus Prevention

Answer 26

Good hygiene, vaccines, anti-viral drugs (but not ABX)