LEC EXAM #1 CHP. 6

Question 1

Is a virus a living organism?

Answer 1

No, viruses are considered acellular and needs a host cell/genome to survive

Question 2

What is the general structure of a virus?

Answer 2

• Extremely small
• Bacteriophage structure
• Capsid protein coat that protects viral genome
• Has spikes that binds to host cell receptor

Question 3

Enveloped virus:

Answer 3

-Contains genetic material, capsid and lipid bilayer surrounding capsid

Question 4

Naked/non-enveloped virus:

Answer 4

• No surrounding bilayer

- Contains only genetic material and capsid

Question 5

Outer shell of a virus is made of?

Answer 5

Capsomeres that make up capsid

Question 6

How are viruses grown in the laboratory?

Answer 6

Viruses can be grown in a host (in vivo) or in a petri dish, or flask (in vitro).

Question 7

How are animal viruses identified in the lab?

Answer 7

Virus is grown in vivo (inside the cell) and the cell is observed for cytopathic effects

Question 8

Mycoplasma vs. viral particles

Answer 8

Mycoplasmas have the ability to replicate their own genome

Viral particles have to use host cell to replicate

Question 9

Mycoplasmas contain:

Answer 9

Cholesterol in their cell membrane

Question 10

Where do mycoplasma cells enter the body first?

Answer 10

Mucosal cell in genitals

Question 11

Mycoplasma characteristics: (6)

Answer 11

• No cell wall
• Smallest known living organism
• Pleomorphic
• Contains cholesterol + other sterols in cell membrane
• Can survive inside cells
• Found in soil, plants, and animals

Question 12

Goal of capsid:

Answer 12

To protect genome in cell

Question 13

Spikes help with:

Answer 13

Attachment to the host cell in BOTH enveloped and non-enveloped viruses

Question 14

What do bacteriophages do?

Answer 14

Replicate genetic material and proteins

Question 15

Spikes are made of:

Answer 15

Glycoproteins

Question 16

Spikes on capsids are:

Answer 16

Sheath and tail fibers that attaches and inserts genomes into host cells

Question 17

Capsid in both enveloped and non-enveloped can cause:

Answer 17

Immune response

Question 18

How do bacteriophages replicate in prokaryotic host?

LYTIC CYCLE

Answer 18

Attachment to cell-> infects by penetration of genome-> host DNA destroyed-> new phage particles are made -> lyses and kills cell

Question 19

Lytic and lysogenic cycle: (temperate phage)

Answer 19

Attachment to cell-> phage DNA integrates itself with host DNA-> cell replicates-> under stressful condition phage pops out of genome and produces its parts-> goes through lytic cycle-> lyses and kills cell

Question 20

Viral infection of eukaryotic host cell: lytic cycle

Answer 20

• Entry is either by endocytosis for non-enveloped or membrane fusion for enveloped
• Attachment of virus
• Penetration of virus into membrane
• Uncoating of viral contents
• Biosynthesis: RNA enters nucleus and is replicated by RNA polymerase
• Assembly of new phage particles
• Release of viral particles into EXF but host cell does NOT die

Question 21

Family ends in:

Answer 21

-virdidae

Question 22

Genes end in:

Answer 22

-virus

Question 23

What is the filter porte size for viral isolation from bacterial particles?

Answer 23

0.2 microns

Question 24

Viral classification of +ssRNA and -ssRNA:

Answer 24

+ssRNA (sense strand)

-ssRNA (anti-sensens strand that is complimentary to sense strand)

Question 25

Goal of temperate phage:

Answer 25

To incorporate DNA into host cells DNA

Question 26

In latent infection:

Answer 26

Viral loads increased

Question 27

In viral growth:

Answer 27

Viral loads deceased

Question 28

HeLa cells by:

Answer 28

Henrietta Lax

Question 29

Antibodies are specific for spikes on specific viruses. T or F

Answer 29

True

Question 30

What process happens in HIV?

Answer 30

HIV binds GP120 to CD4-> causes it to bind to coreceptor CCR5-> fusion of membranes + viral genetic material inserted into host cell-> dumps reverse transcriptase, integrase, and RNA into host cell-> viral DNA is formed from viral RNA via reverse transcription-> viral DNA combines with integrase to go into nucleus to make viral proteins (capsids and spikes) and viral proteins come out to get used or packaged-> buds off to infect other cells

Question 31

Viruses enter eukaryotic host cell via:

Answer 31

Endocytosis for non-enveloped viruses or membrane fusion for enveloped viruses

Question 32

How are viruses treated?

Answer 32

With antiviral drugs that interfere with some parts of their "life cycles"

Question 33

What are some cytopathic effects of viruses on human/animal cells? (7)

Answer 33

- Loss of adherence to surface - Changes in cell shape from flat to round - Shrinkage of nucleus - Vacuoles in cytoplasm - Formation of cytoplasmic membrane and formation of mutlinucleated syncytial - Inclusion bodies in the nucleus or cytoplasm - Complete cell lysis

Question 34

What is generalized transduction?

Answer 34

- Transfer and packaging of pure DNA into the virus | - Lytic cycle

Question 35

What is specialized transduction?

Answer 35

- Transfer and packaging of small percentage of bacterial DNA with the viral DNA genome - Lysogenic cycle

Question 36

Steps of generalized transduction?

Answer 36

- Phage infects bacterial cell - Phage DNA replicates and bacterial DNA is fragmented/hydrolyzed into small pieces - During assembly, bacterial DNA fragment accidentally gets packaged into a phage head - New phages lyse out and kill cell - Phages infect other cells, some of these have bacterial genes that they donate to the new host cell= crossing over of genes

Question 37

Steps of specialized transduction?

Answer 37

- Phage infects bacterial cell - Integrates its DNA with bacterial DNA - Host cell with phage DNA + bacterial DNA replicates into daughter cells - Phage remains dormant until stressful condition arises * Goes through lytic cycle* - Phage destroys bacterial DNA and replicates its DNA but has some bacterial DNA parts in it - Phage DNA is packaged with bacterial DNA - Phages lyse out and kill cell - Phages infect other cells with mixed DNA-> donates genes to a new host cell= crossing over of genes

Question 38

Difference between packaging processes in generalized and specialized transduction?

Answer 38

In generalized transduction, bacterial DNA is packaged separately from phage DNA In specialized transduction, bacterial DNA is MIXED with phage DNA

Question 39

If you have a -ssRNA virus, what must it do to its genome before it can start making proteins/proteins?

Answer 39

Make its +ssRNA compliment

Question 40

Double stranded RNA have:

Answer 40

BOTH + and -

Question 41

Single stranded RNA have:

Answer 41

+ OR -

Question 42

RdRP:

Answer 42

RNA polymerase that does transcription of any - strand and makes it into + strand to make proteins

Question 43

+ssRNA is used:

Answer 43

By the host cell's 80s ribosome to make viral proteins (spikes and capsids) OR Make more -ssRNA for new viral particles

Question 44

What is responsible for converting RNA into DNA?

Answer 44

Reverse transcriptase

Question 45

In acute infection:

Answer 45

Viral load increases immediately

Question 46

In persistant infection:

Answer 46

Viral load increases consistently over time

Question 47

Viral growth steps: (4)

Answer 47

1. inoculation: inoculum of virus binds to cell 2. eclipse: virions penetrate the cell 3. burst: host cells release many viral particles 4. burst size: number of visions released per bacterium

Question 48

Antibodies are specific for the spikes on a specific virus: T or F

Answer 48

TRUE

Question 49

Direct assay:

Answer 49

Spikes cause hemagglutination of virus and RBC

Question 50

Indirect assay:

Answer 50

No hemagglutination because antibodies bind to virus-> virus can't bind to RBC