Ch.13 Viruses, Viroids & Prions Part 2

Question 1

what are the steps to animal virus infection?

Answer 1

1. attachment
2. Entry
3. Uncoating
4. synthesis & replication
5. Assembly
6. Release

Question 2

What occurs in attachment in an animal virus?

Answer 2

to host protein, & glycoprotein receptor sites

Question 3

what occurs in the entry step in animal virus infection?

Answer 3

fusion (enveloped viruses)

receptor-mediated endocytosis

Question 4

what occurs in the uncoating step in animal virus infection?

Answer 4

separation of the genome of the internalized virus from its capsid

can occur at the cell membrane or the nuclear membrane

Question 5

what do animal viruses use to form in the host cytoplasm to form proteins?

Answer 5

ribosomes

Question 6

where does the assembly of new virions (capsid, genome) occur?

Answer 6

in the cytoplasm or nucleus

Question 7

how are virions released from the host?

Answer 7

lysis or budding

Question 8

where are envelope proteins inserted into?

Answer 8

into the plasma membrane or organelle membrane

Question 9

where does genome replication occur in DNA viruses?

Answer 9

nucleus

Question 10

where does the synthesis of viral protein occur in DNA viruses?

Answer 10

outside of nucleus

Question 11

where do viral proteins enter in DNA viruses?

Answer 11

into nucleus

Question 12

where does viral assembly occur in DNA viruses?

Answer 12

nucleus

Question 13

In Rna viruses where does genome replication, synthesis of viral proteins, and viral assembly all occur?

Answer 13

outside of the nucleus

Question 14

DNA viruses in the multiplication of animal viruses utilize what?

Answer 14

utilize the host replication machinery (DNA polymerase)

Question 15

DNA virus genome can serve as

Answer 15

a template for DNA synthesis and transcription

Question 16

what do non-retroviral RNA viruses possess?

Answer 16

RNA-dependent
RNA Polymerase (RDRP)

Question 17

Using the RDRP genome it can serve as a template for?

Answer 17

translation in (+) ss RNA viruses

synthesis of mRNA in (-) ss RNA viruses

Question 18

what do retroviruses possess?

Answer 18

reverse transcriptase (RT)

Question 19

Using reverse transcriptase, the genome can serve as a template for?

Answer 19

DNA synthesis

Question 20

steps to DNA virus infection:

Answer 20

1.Attachemnt: virion attaches to host cell

2. Entry and Uncoating: The virion enters the cell and its DNA is uncoated
3. A portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins
4. Biosynthesis: viral DNA is replicated and some viral proteins are made
5. Late translation: capsid proteins are synthesized

6.Maturation: Virions mature

7. Release: virions are released

Question 21

steps to RNA virus replication:

Answer 21

1. attachment
2. entry and uncoating
3. RNA replication by viral RNA-dependent RNA Polymerase
4. Translation and synthesis of viral proteins
5. maturation & release

Question 22

ssRNA or + sense strand

Answer 22

picornviriade

1. –strand is transcribes from + viral genome
2. mRNA is transcribed from the - strand
3. capsid protein forms & + strand

Question 23

ssRNA or - antisense strand

Answer 23

Rhabdoviridae

1. the + strand (mRNA) must be transcribed from the - viral genome before proteins can be synthesized
2. additional - strands are transcribed from mRNA

3.Capsid protein forms & - strands are incorporated into capsid

Question 24

dsRNA or + sense strand with - or antisense strand

Answer 24

Reoviridae

1.mRNA is produced inside the capsid and released into the cytoplasm of the host

2. Capsid proteins and RNA-dependent RNA polymerase form
   RNA polymerase initiates the production of - strands. The mRNA and - strands form the dsRNA that is incorporated as a new viral genome

Question 25

retrovirus replication steps:

Answer 25

1. an enveloped RNA virus enters by fusion *has 2 identical (+) RNA strands * infects T helper cells of the immune system 2. uncoating releases RNA genome & viral enzymes, including reverse transcriptase to copy viral RNA to form dsDNA 3. DNA integrates into the host genome; forming a provirus(intergrase) 4. may stay in a persistent state while a cell is dividing 5. provirus may be transcribed into RNA; and translated into viral proteins 6. synthesized glycoproteins inserted into the host cell membrane; virus assembly and exit by budding

Question 26

Bacteriophage viral multiplication

Answer 26

1. Attachment: tail fibers attached to cell wall proteins 2. Entry: viral DNA is injected into the host cell 3. uncoating: Not required 4. biosynthesis: in cytoplasm 5. chronic infection: lysogeny 6. release: host cell is lysed

Question 27

Animal viral replication:

Answer 27

1. Attachment: sites are plasma membrane and glycoproteins 2. entry: capsid enters by receptor-mediated endocytosis or fusion 3. uncoating: enzymatic removal of capsid proteins 4:biosytheis: in the nucleus (DNA viruses or cytoplasm (RNA virus) 5. chronic infection: latency; slow viral infections; cancer 6. release: enveloped viruses bud out; nonenveloped viruses rupture the plasma membrane

Question 28

what are prions?

Answer 28

are proteins that infect animals; they have no nucleic acid component

Question 29

what do prions cause?

Answer 29

degenerative brain disease ("mad cow" disease) Creutzfield-Jacob disease in humans scapie kuru

Question 30

how are prions transmitted?

Answer 30

in food, prepared from infected animals

Question 31

what does prion disease do?

Answer 31

converts a normal brain cell glycoprotein (Prp^c) into an infectious form PrP^sc PrP^Sc molecules accumulate in the brain, forming plaques (cavities)

Question 32

what are prions resistant to?

Answer 32

physical & chemical agents

Question 33

what are viroids?

Answer 33

are not viruses are naked RNA molecules that lack a capsid RNA does not encode for proteins (300-400) nucleotides long

Question 34

what do viroids infect?

Answer 34

plants

Question 35

how are viroids replicated?

Answer 35

by host RNA polymerase

Question 36

what do some viroids have?

Answer 36

catalytic ability

Question 37

what are latent viral infections?

Answer 37

virus that infects host cell but does NOT cause disease; can remain in a dormant state for long periods

Question 38

what can activate a latent infection?

Answer 38

Immunosuppression or stress

Question 39

what are some examples of latent infections?

Answer 39

oncogenic viruses herpes viruses chicken pox(shingles)

Question 40

what are persistent(chronic) viral infections?

Answer 40

occur gradually over a long period; typically are fatal

Question 41

what is continuously released in persistent(chronic) viral infections?

Answer 41

viruses

Question 42

examples of persistent(chronic) viral infections?

Answer 42

HIV-1, 2 papillomavirus Hepatitis B Virus

Question 43

describes lytic cycle:

Answer 43

t even phages are virulent phage quickly replicates killing the host cell(lytic burst)

Question 44

describe the lysogenic cycle:

Answer 44

lambda phage temperate phages do not necessarily kill the host immediately integrates into cell chromosomes as a prophage can reactivate to become lytic environmental cues dictate when lysogeny converts to the lytic cycle

Question 45

The lytic cycle of phage T4

Answer 45

1. attachment: to specific cell surface proteins 2. Penetration: viral nucleic acid entering cell/ degradation of host DNA 3. Biosynthesis: Viral DNA & viral proteins The eclipse period between the degradation of host DNA and maturation 4. Maturation 5. Release: lysis of host cell wall by lysozyme

Question 46

Lysogenic viral DNA integrating into the host genome is what?

Answer 46

prophage

Question 47

transduction may result in what?

Answer 47

phage conversion