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Exam 3 And Final Microbiology > Viruses > Flashcards

Viruses Flashcards

1
Q

What is a virus?

A

A virus is a non-cellular particle that must infect a host cell to reproduce

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2
Q

Viruses
– are obligatory _________ __________
– that take over the _______ _______ ______ and direct the cell to produce more virus particles.

A
  • obligatory intracellular parasites
    – the infected cell’s machinery
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3
Q

A virus particle (______), consists of nucleus acid (___ or ___) contained within a protective coat called a _______

What do they not contain?

A
  • Virion
    -DNA or RNA
    -capsid

-do not contain ribosomes or ATP generating machinery

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4
Q

What are the 6 general characteristics of viruses?

A
  1. Most viruses are very small
  2. Viruses contain nucleic acid (DNA or RNA)
  3. Nucleic acid is packaged in a protein coat (capsid)
  4. Some viruses are enclosed in an envelope
  5. Some viruses have spikes
  6. Each species of virus infects a particular group of host species, called the host range
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5
Q

What size is most viruses?

A

50-100 nm

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6
Q

Nucleic acid can be:

A

• DNA or RNA
• Single or double-stranded
• Circular or linear

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7
Q

The virus “genome” is usually very small and usually encodes only a few genes.
Name these 3 genes:

A

• Capsomere (capsid subunits)
• Envelope proteins (if enveloped virus)
• Polymerase (if special polymerase needed)

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8
Q

How many protein coding genes does Influenza A virus have?

A

11 coding genes

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9
Q

The nucleic acid is packaged in a protein coat called the _____

A

Capsid

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10
Q

Capsid is made of repeating protein subunits called _______. What do they do?

A

•capsomeres
• package and protect viral genome

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11
Q

Some viruses are enclosed in an envelope. What is an envelope?

A

bilayer that surrounding capsid, derived from the host cell membrane

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12
Q

What are enveloped viruses more sensitive to?

A

Heat or detergents

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13
Q

Virus have spikes. What are spikes? What are they involved in?

A

• The spikes are glycoproteins (carbohydrate-protein complexes) in the envelope.
• Spikes are involved in attachment to a host cell and escape from a host cell

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14
Q

Each species of virus infects a particular set of host’s. What can they infect?

A

• Bacteria
• Fungi
• Protozoa
• Plants
• Animals
Most viruses can only infect a specific type of cells within a single host species

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15
Q

What does the HIV virus infect?

A

HIV (virus) infects T cells (cell type) in humans (host species)

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16
Q

(Define)
- Host Range:
- Tissue tropism:

A

• Host range: set of species that a particular virus can infect
• Tissue tropism: tissue and/or cell type that virus can infect

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17
Q

Host range and tissue tropism are generally determined by what?

A

specific host attachment sites on the virus (spikes) and the presence of specific receptors on the host cell

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18
Q

There are 5 steps of Viral Replication (Viral Life Cycles)
What are the steps and give a small description of them:

A
  1. recognition/ attachment
    • Viruses must contact and adhere to a host cell that can support replication of specific virus
  2. entry
    • The viral genome must enter the host cell and gain access to the host cell’s machinery for gene expression
  3. Biosynthesis
    • Includes synthesis of both viral genome and virus-specific proteins
  4. Assembly of virions
    • Components usually self-assemble spontaneously.
  5. Exit and transmission
    • Progeny virions must exit the host cell and reach new host cells and, if multicellular, new hosts to infect
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19
Q

Bacteriophage are viruses that infect bacteria. What kind of temperatures do they withstand? What shape do they have?

A

They are mostly mesophilic and mildly thermophilic.
Icosahedral head-filamentous tail shape

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20
Q

What are the 5 steps of the lytic cycle of a bacteriophage (Describe each briefly)

A
  1. Attachment: Phage attaches to host cell
  2. Penetration: Phage penetrates and inserts DNA into host cell
  3. Biosynthesis: Production of phage DNA and phage proteins by the infected cell
  4. Maturation: Self-assembly of phage particles; virus genome is packaged into capsid
  5. Release: Phage degrades infected host cell wall; host cell lyses (bursts); new phage particles are released
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21
Q

Define transduction

A

Transduction is the transfer of DNA from one bacterial cell to another bacterial cell by a bacteriophage

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22
Q

Generalized transduction involves the ______ life cycle of the phage and can move any _____

A

Lytic life cycle
Gene

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23
Q

(Define)
Virulent phage:
Temperate phage:

A

• Virulent phage: reproduce only through the lytic cycle, resulting in lysis of the host bacterial cell
– Ex: phage T4
• Temperate phage: can reproduce through the lytic cycle; can also undergo lysogeny, where the phage genome inserts into the host genome
– Ex: phage lambda

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24
Q

What are the 5 steps of the Lysogenic Cycle of a bacteriophage? (Give brief description of each)

A
  1. Attachment: Phage attaches to host cell
  2. Penetration: Phage inserts DNA into host cell
  3. Integration: Phage DNA integrates into bacterial chromosome by recombination; the integrated phage DNA is called a prophage
    – expression of phage genes is repressed
    – “lysogenic bacterium” divides normally; prophage is maintained in the
    bacterial chromosome
    -Phage may carry genes that give host cell an advantage
  4. Excision: Prophage excises from chromosome (phage induction); excision can be stimulated by UV or chemical
  5. Lytic cycle: Excised phage enters lytic cycle
25
Q

Specialized transduction involves the _______ life cycle. Moves only genes connected to site of _______ _______

A

Lysogenic cycle
Prophage insertion

26
Q

What are The 6 steps of the General Life Cycle of Animal Viruses?

A

• Attachment:virus attaches to host cell membrane
2. Penetration: virus enters host cell by endocytosis or fusion
3. Uncoating:capsid removed by viral host enzymes
4. Biosynthesis: infected host cell produces viral nucleic acid and viral proteins → * may require viral enzymes* (IMPORTANT)
5. Maturation (or Assembly): viral nucleic acid and viral capsid proteins assemble into virus particle
6. Release: virus escapes host cell-by budding (enveloped viruses), exocytosis, or rupture (lysis)

27
Q

What are the 3 primary factors determining the life cycle of an animal virus:

A

DNA viruses (uses host replication machinery)

RNA viruses causes an RNA dependent RNA polymerase to copy their RNA)

Retroviruses

28
Q

Retroviruses use a _______ ________ to copy the RNA genome into DNA and an ______ to insert the DNA into the host chromosome

A

Reverse transcriptase
Integrase

29
Q

All viruses required host cell for ________

A

Reproduction

30
Q

What is HPV’s full name?

A

Human papillomavirus

31
Q

HPV
Small _______ virus, envelope or no envelope?
Describe the genome:
How many coding genes?

A

Small icosahedral virus
No envelope
Genome: small, circular, d.s. DNA
- 8 kb, encoding 8 genes

32
Q

(HPV disease)
Does it go away? Does it need treatment?
Infects _______ cells —-> causes _____ _____
HPV can also integrate into genome of host basal cells (“_____”, similar to Lysogeny) can cause cancers. But what kind?

A

Can go away on its own
Infects epithelial cells, causes general warts
“Latent” similar to lysoginy
Can cause cervical, penis, anus and throat cancer

33
Q

HPV (Disease)
How is it transmitted?
How is it prevented?
How many adults are infected with HPV in the U.S?

A

Direct contact (sex)
Gardasil hpv vaccine, recommended for girls/boys at age 11-12
80% of adults

34
Q

HPV
Papillomavirus: DNA genome
1. Virion attaches to host cell and is ______
2. Virion travels to ______
3. Viral genome is _______
4. Biosynthesis uses host enzymes. Viral DNA is _____ (nucleus) and translated (______) to produce _____ proteins
5. Assembly occurs in ______
6. Release, Virion are shed as ______ _______ slough off

A
  1. Endocytosed
  2. Nucleus
  3. Uncoated
  4. Transcribed (nucleus) and translated (cytoplasm) to produce (capsid) proteins
  5. Nucleus
  6. Epithelial cells
35
Q

Viruses are responsible for ~____ - ____% of human cancers

A

-15-20%

36
Q

What cancers do these viruses cause?
- Epstein-Barr virus
-Human papillomavirus (HPV; papilloma – wart)
- Hepatitis B
- Human Herpes Virus-8

A

• Epstein-Barr virus
-Burkitt’s lymphoma; Hodgkin’s disease
• Human papillomavirus (HPV; papilloma – wart)
-Cervical cancer, head and neck cancers; anogenital cancers
• Hepatitis B virus
-Liver (hepatocellular) cancer
• Human herpes virus-8
-Kaposi’s sarcoma

37
Q

What are the RNA viruses that contribute to cancer?

A

Human t-cell leukemia virus
Hepatitis C virus - liver (hepatocellular) cancer

38
Q

Influenza A virus
(-) or (+) strand RNA virus? _____ genome
______ virus with spikes

A

(-) negative strand RNA virus, segmented genome
Enveloped virus with spikes

39
Q

Influenza A virus (disease)
What kind of infection?
Symptoms?
Who does it affect?
___% (36,000) of US population infected every year
How many deaths world wide each year?
Global pandemics, e.g. Flu of 1918 infected ~20% of the world
population, ____ - ______ million deaths worldwide

A

Upper respiratory infection
Sore throat, headache, resolves in <2 weeks
Affects elderly, very young, immune compromised people
-10%
50-100 million deaths per year

40
Q

Influenza A virus (Disease)
Transmission?
Prevention?
Treatment?

A

Droplets ( sneezing, coughing)
Seasonal flu vaccine, hand washing
Tamiflu, Zanamivie (inhibits neuraminidase)

41
Q

How many coding genes does Influenza A virus have?

A

-11 protein-coding genes on 8 separate RNA molecules

42
Q

Influenza A viruses
How many “h” hemaggluttinin proteins does it have?
How many “N” Neuraminidase proteins dots it have?

A

– “H”: hemagglutinin protein (HA); 16 subtypes; lectin involved in attachment to host cell
– “N”: neuraminidase protein (NA); 9 subtypes; enzyme involved in release from host cell

43
Q

What do these stand for?
• RdRP
• +ssRNA
• -ssRNA

A

RdRP= viral independent RNA polymerase
+rrRNA= positive (+) single strands
-ssRNA= negative (-) single strand RNA

44
Q

What are antibodies?

A

Antibodies are proteins produced by the host(e.g. human) that bind to specific antigens (parts of the pathogen); antibody binding to an antigen stimulates many aspects of the immune response

45
Q

RNA dependent RNA polymerase makes approx 1 mistake per _____nt
Influenza A virus genome ~ ______ nt
Every copy generally contains a ______

A

10,000 nt
14,000 nt
Mutation

46
Q

What is an antigenic drift?

A

gradual change in surface molecules of virus (e.g. HA and NA spikes)
→ host antibodies may not recognize altered antigens ( IMPORTANT)

47
Q

What are the 6 steps of influenza A virus replication cycle?

A
  1. Attachment
  2. Penetration
  3. Uncoating
  4. Biosynthesis
  5. Assembly
  6. Release
48
Q

_____% virus particles are assembled correctly; moody new virus particles are defective

A

<1 %

49
Q

A single infected cell can produce _______ virus particles

A

10,000

50
Q

_______ of genome segments from different viral strains infecting the same host at the same time can generate new viral strains

A

Reassortment (mixing of 2 different viruses or more to create new virus)

51
Q

Define antigenic shift

A

reassortment (mixing) of genome that occurs when two different viruses infect the same host at the same time – can result in fast, dramatic change in antigens (surface spike)

52
Q

What is the full name of HIV

A

human immunodeficiency virus

53
Q

HIV retrovirus (Disease)
Causes?
Infects _____ cells
Progressive loss of immune system leads to:

A

•Causes AIDS, immune deficiency syndrome
• HIV infects CD4+ T cells
• progressive loss of the immune
system leads to opportunistic infections and cancers

53
Q

HIV retrovirus (Disease)
Causes?
Infects _____ cells
Progressive loss of immune system leads to:

A

•Causes AIDS, immune deficiency syndrome
• HIV infects CD4+ T cells
• progressive loss of the immune
system leads to opportunistic infections and cancers

54
Q

HIV (disease)
____million people infected with HIV
___ million deaths per year
Is it equal between men and women?

A

33 million
3 million
Yes equal between men/women

55
Q

HIV (disease)
Transmission?
Cure?

A

Contact with bodily fluids
Variety of treatments but no cure

Azidothymidine (AZT): nucleoside reverse transcriptase inhibitor (NRTI)

56
Q

What are the 3 proteins in retrovirus HIV?

A

Matrix, nucleocapsid(bonds to RNA genome), capsid

57
Q

What are the 3 enzymes in retrovirus HIV?

A

Protease, reverse transcriptase, integrase

58
Q

Hiv-1 genome consists of:
1. Gag 2. Pol 3. Env
Describe each of these

A
  1. Gag-encodes capsid, nucleocapsid and matrix
  2. Pol- encodes reverse transcription (RT), integrase, protease (encodes enzymes)
  3. Encodes envelope (spike) proteins (envelope)

Exam 3 And Final Microbiology (10 decks)

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