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MICROBIO BIOL-160 LEC > Viruses > Flashcards

Viruses Flashcards

1
Q

describe the DEFINITION OF LIFE and how VIRUSES play into said definition?

A
  • can be INERT OUTSIDE A HOST–have VIRAL NUCLEIC ACIDS that ARE ACTIVE
  • does not respire
  • does not respond to stimuli
  • does not grow

BUT THEY CAN REPRODUCE and ADAPT TO NEW HOSTS
- can begin to DISPLAY THE MOST ESSENTIAL ATTRIBUTES OF A LIVING THING through replication
- can INFECT A HOST

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2
Q

definition of VIRUSES

A
  • ACELLULAR ORGANISMS whose GENOMES consist of NUCLEIC ACIDS
  • can be seen in DNA or RNA
  • use and replicate INSIDE HOST CELLS by using HOST METABOLIC MACHINERY
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3
Q

what do VIRUSES NOT DO? (7)

A
  • they CANNOT CARRY OUT METABOLIC ACTIVITY
  • they CANNOT REPRODUCE INDEPENDENTLY
  • they DO NOT HAVE MEMBRANE BOUND ORGANELLES
  • NO CELLULAR MEMBRANE
  • they DO NOT GROW IN SIZE OR RESPOND to their DIRECT ENVIRONMENT
  • they DO NOT FOLLOW THE CENTRAL DOGMA
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4
Q

the more PROPER DEFINITION OF A VIRUS

A
  • an INFECTIVE AGENT CONSISTING OF NUCLEIC ACIDS that is surrounded by a PROTEIN COAT and is only CAPABLE OF REPLICATION within the LIVING CELLS of BACTERIA, ANIMALS, or PLANTS
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5
Q

describe the TYPICAL VIRUS and its INTRACELLULAR/EXTRACELLULAR STATES

A
  • they are SUB MICROSCOPIC–can only use ELECTRON MICROSCOPES to see them
  • ACELLULAR (NO ORGANELLES)
    [also have NUCLEIC ACIDS and CAPSID ENCLOSURES (protein coats)]
  • can be INFECTIOUS

INTRACELLULAR STATES:

  • known as a VIRUS

EXTRACELLULAR STATES:

  • known as a VIRION
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6
Q

describe the CHARACTERISTICS OF EXTRACELLULAR (VIRION) and INTRACELLULAR (VIRUS)

A

VIRION

  • has a PROTEIN COAT (CAPSID)
  • has RECOGNITION for HOST
  • can have a PHOSPHOLIPID COVER (ENVELOPE)

VIRUS

  • NO CAPSID PRESENT
  • has REPLICATION STAGE
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7
Q

describe a VIRUS GENOME SIZE

A
  • E. Coli GENOME around 4.5 - 5.5 million BP
  • VIRUSES around 30,000 - 300,000 BP
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8
Q

describe the VIRAL GENOME

A
  • can be DNA or RNA (BUT NEVER BOTH)
  • can be SINGLE STRANDED (ss) or DOUBLE STRANDED (ds)
  • can be MULTIPLE vs. SINGLE

ARRANGEMENT:
- can be either LINEAR OR CIRCULAR

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9
Q

describe DNA VIRUSES

A
  • they are NON-SEGMENTED (all in ONE PIECE)
  • can be LINEAR or CIRCULAR
  • can be ds or ss
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10
Q

describe RNA VIRUSES

A
  • can be NON SEGMENTED or SEGMENTED
  • can be LINEAR or CIRCULAR
  • can be ds or ss
  • if SS; can be either - or + sense
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11
Q

describe RNA VIRUSES – (-) or (+) SENSE

A

SENSE (+)

  • similar to mRNA–directs the PRODUCTION OF PROTEIN

SENSE (-)

  • MUST BE CONVERTED INTO POSITIVE STRAND to PRODUCE PROTEINS
  • use of a COMPLEMENTARY TO TEMPLATE STRAND
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12
Q

describe VIRAL SIZE

A
  • can be only up to 10 nm to 400 nm
    (nm - 10^-9 meter)
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13
Q

describe CAPSID and their function

A
  • has REPETITIVE UNITS of ONE OR FEW PROTEINS that are known as CAPSOMERES

FUNCTIONS:

  • PROTECTION
  • ATTACHMENT and PENETRATION of HOST CELL
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14
Q

describe VIRAL MORPHOLOGY

A

HELICAL/TUBE:

  • has LONG RODS
  • RIGID and FLEXIBLE

POLYHEDRAL:

  • most are ICOSAHEDRONS–POLYHEDROM with 20 triangular faces and 12 corners

COMPLEX:

  • can be complicated
  • has CAPSIDS with structures attached
  • ex. BACTERIOPHAGE
  • can also be ENVELOPED–surrounded by a membrane
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15
Q

describe a VIRUS ENVELOPE

A
  • typically SPHERICAL
  • can have ENVELOPED HELICAL VIRUSES
  • can have ENVELOPED POLYHEDRAL
  • has a SIMILAR COMP to a CELLULAR MEMBRANE
  • often has VIRAL GLYCOPROTEINS to help AVOID the IMMUNE SYSTEM and secure host binding
  • is the VIRAL PROTECTION MECHANISM
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16
Q

what can VIRUSES INFECT?

A
  • ALL CELLULAR ORGANISMS can be INFECTED–ALL THREE DOMAINS
  • ANIMALS, PLANTS, FUNGI, and BACTERIA
  • can be EITHER be SPECIES SPECIFIC/NARROW HOST RANGE (ex. smallpox) or have a BROAD RANGE (ex. rabies)
  • work by RECOGNITION OF SPECIFIC RECEPTOR SITE
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17
Q

how are VIRUSES CLASSIFIED/

A
  • based on the SYMPTOMS OF DISEASES caused by the VIRUS
  • use of INTERNAL COMMITTEE on TAXONOMY OF VIRUSES (ICTV)
  • based on genomics and structure
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18
Q

definition of VIRAL SPECIES

A
  • a GROUP OF VIRUSES that SHARE THE SAME GENETIC INFORMATION and HOST RANGE
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19
Q

describe the BASIC STAGES of VIRAL REPLICATION

A
  1. ATTACHMENT
    locate and stick
  2. ENTRY
    getting in
  3. SYNTHESIS
    making pieces
  4. ASSEMBLY
    putting it together
  5. LYSIS
    getting out
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20
Q

what are the FIVE STEPS of the LYTIC CYCLE

A
  1. ATTACHMENT
  2. ENTRY
  3. SYNTHESIS
  4. ASSEMBLY
  5. LYSIS
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21
Q

describe ATTACHMENT (1) of the LYTIC CYCLE

A
  • begins with a CHANCE ENCOUNTER between BACTERIUM and PHAGE
  • certain attraction between the phage’s TAIL FIBERS and PROTEINS ON THE BACTERIUM
  • can either attach to the CELL WALL, FLAGELLUM, and PILUS (*if they land on the flagellum or pilus–will continue moving until reaching the cell wall)
22
Q

describe ENTRY (2) of the LYTIC CYCLE

A
  • TAIL will then release the enzyme PHAGE LYSOZYME to BREAK DOWN CELL WALL
  • TAIL SHEATH is contracted and TAIL CORE is DRIVEN INTO CELL WALL AND MEMBRANE
  • VIRAL DNA and ENZYMES MOVE IN THROUGH TAIL CORE
  • CAPSID IS OUTSIDE OF CELL STILL
23
Q

describe SYNTHESIS and ASSEMBLY (3-4) of LYTIC CYCLE

A
  • VIRAL DNA TAKES OVER–TURNS OFF SYNTHESIS OF BACTERIAL COMPONENTS to then make PHAGE COMPONENTS
  • reaches MATURATION:
    cell is now COMPLETELY FULL of VIRAL COMPONENTS–with capsids and nucleic acids to make VIRAL PARTICLES
24
Q

describe RELEASE (5) of the LYTIC CYCLE

A
  • CELL NOW LYSES and NEW VIRONS ARE RELEASED
  • can also be EATEN
25
Q

definition of BURST TIME and BURST SIZE

A

BURST TIME:

  • the time from attachment to release
  • the amount of time of replication

BURST SIZE

  • amount of quantity
26
Q

describe the BASIC STEPS OF LYSOGENIC REPLICATION

A
  1. ATTACHMENT
  2. ENTRY
27
Q

describe LYSOGENY and LYSOGENIC CYCLE IN GENERAL

A
  • really cool because there is only TWO STEPS INVOLVED–ATTACHMENT AND ENTRY
  • has POST ENTRY–NO SYNTHESIS STEP
  • the PHAGE DNA begins to INTEGRATE INTO BACTERIAL CHROMOSOME–known as PROPHAGE
  • turns DORMANT AND INACTIVE
28
Q

definition of INDUCTION

A

occasional environmental factors that begin to TRIGGER THE EXCISION of DNA and START A LYTIC CYCLE

29
Q

what are the THREE IMPORTANT CONSEQUENCES of LYSOGENY?

A
  1. HOST IS IMMUNE TO REINFECTION BY SAME VIRUS
  2. PHAGE CONVERSION–host cell can have new properties such as picking up TOXIN GENES on PROPHAGE
  3. TRANSDUCTION–the TRANSFER OF BACTERIAL GENES from ONE BACTERIA TO ANOTHER
30
Q

briefly describe LYSOGENIC CYCLE

A
  1. Phage attachment and injection of DNA
  2. Phage DNA turns CIRCULAR
  3. begins to INTEGRATE INTO BACTERIAL CHROMOSOME–prophage (by RECOMBINATION)
  4. continuation of NORMAL BACTERIAL REPRODUCTION with the PHAGE DNA ALREADY INTEGRATED
  5. will be OCCASIONALLY ACTIVIATED by either INDUCTION or triggering event etc…
31
Q

describe TRANSDUCTION

A

process of where PHAGE GENOME IS EXCISED and carries a small part of normal HOST CELL GENE–often can give NEW GENES to unaffected BACTERIUMS
- now has integration of new ability–ex. METABOLISM of certain COMPONENT

32
Q

describe ANIMAL VIRUSES–ATTACHMENT and ENTRY

A

CAPSID MORPHOLOGY
- can have NO TAILS–either NAKED or ENVELOPED

HOST TYPE:
- attaches to specific RECEPTOR ON HOST CELL
- RECEPTOR SITES–are PROTEINS and GLYCOPROTEINS in CELL MEMBRANE

33
Q

describe ENTRY METHODS of ANIMAL VIRUSES

A

DIRECT PENETRATION

  • seen in NAKED VIRUSES
  • INJECTION OF DNA INTO CELL
  • RESTRICTED ONLY TO VIRUSES that only their GENOME TO INFECT CELL

MEMBRANE FUSION

  • seen in ENVELOPED VIRUSES
  • have MEMBRANE LAYER INTERACTION–fused into membrane itself

ENDOCYTOSIS

  • seen in ENVELOPED VIRUSES
  • HOST-CELL EATING is triggered–have the CYTOPLASMIC MEMBRANE ENGULF the VIRUS
34
Q

describe SYNTEHSIS within the LYSOGENIC CYCLE

A

ENTRY
- use of GENETIC MATERIAL and ACCESSORY PROTEINS

GENETIC MATERIAL

  • CODES NEEDED PROTEINS
  • serves as a TEMPLATE

PROTEINS

  • can ADAPT and REPLICATE the GENETIC MATERIAL
35
Q

what are the TYPES OF GENETIC MATERIAL USED within ANIMAL VIRUSES

A
  • GENETIC MATERIAL can be COPIED AND ADAPTED

GENETIC MATERIAL:

  • ds DNA
  • ss DNA
  • ssRNA (+) or - antisense
  • ds RNA
36
Q

briefly describe the CENTRAL DOGMA

A

DNA

  • carrier of GENETIC INFO
  • replicated to pass on INFO
  • transcribed into mRNA

mRNA

  • the MESSSENGER of INFO
  • translated into PROTEIN

PROTEINS

  • structure, carriers and enzymes that MAINTAIN LIFE
37
Q

describe REPLICATION of a DNA CONTAINING ANIMAL VIRUS

A
  • begins with ATTACHMENT OF THE VIRION–and when entering the DNA IS UNCOATED
  • VIRAL DNA then is TRANSCRIBED and encoding to make EARLY VIRAL PROTEINS through mRNA
  • code is then TRNASLATED and capsid proteins are synthesized until the VIRIONS BEGIN TO MATURE and LEAVE THE CELL
38
Q

describe VIRAL GENOME REPLICATION: (+) ssRNA VIRUS and (-) ssRNA VIRUS

A

(+) RNA ha specific gene for RdRP (RNA DEPENDENT RNA POLYMERASE)
- can COPY RNA into a COMPLEMENTARY NEGATIVE SENSE RNA STRAND or vice versa
- RIBOSOME within cell begins to TRANSLATE RNA STRANDS into PROTEINS and begins to ASSEMBLE

39
Q

why is RdRp so important?

A

**RdRp really important because PROKARYOTES and EUKARYOTES CANNOT COPY from RNA to RNA

40
Q

describe VIRAL GENOME REPLICATION: ds RNA VIRUS

A

we now have a DOUBLE STRANDED RNA VIRUS
- will now begin to UNWIND into -ssRNA and +ssRNA STRAND
- -ssRNA STRAND undergoes TRANSCRIPTION by RdRp to make proper COMPLEMETANRY RNA STRANDS
- +ssRNA just acts as mRNA
- together converge to TRANSLATE into VIRAL PROTEINS and then ASSEMBLE

41
Q

describe RETROVIRUSES

A
  • can carry REVERSE TRANSCRIPTASE–specific ENZYME that uses VIRAL RNA to make a COMPLEMENTARY DOUBLE STRANDED DNA
  • VIRAL DNA can now ENTER HOST CHROMOSOME as a PROVIRUS–protected from the HOST IMMUNE SYSTEM–so in turn of that–it can never come out
42
Q

describe ASSEMBLY and RELEASE of ANIMAL VIRUSES

A
  • have similar assembly methods–either NUCLEAR or CYTOSOLIC

RELEASE:

  • either by BUDDING (with or without an envelope)
  • or LYSIS/LYTIC CYCLE
43
Q

definition of LATENCY and consequences of PROVIRUSES

A

LATENCY:

  • the LYSOGENY of a PHAGE

PROVIRUSES:

  • do NOT COME OUT
  • can INHABIT HOST OF YEARS with NO SYMPTOMS
  • any changes in immune system can cause activation and acute infections–ex. shingles
44
Q

what is CANCER caused by?

A
  • abnormal CELL DIVISION
  • often due to VIRAL LYSOGENY/LATENCY
45
Q

definition of ONCOGENES

A

genes whose disruption causes cancer
- CHEMICALS
- RADIATION
- VIRUSES

46
Q

definition of ONCOGENIC VIRUSES

A

viruses that can INDUCE TUMORS

  • can have IRREGULAR SHAPE, ANTIGENS, and CHROMOSOMAL ABNORMALITIES
47
Q

what are some ONCOGENIC VIRUSES?

A

Cervical cancer – HPV
Head and neck cancer – HPV
Liver cancer – Hepatitis B
T cell Leukemia – HTLV
Lymphoma - EBV, HIV

48
Q

how do we GROW VIRUSES?

A
  • MATURE ORGANISMS
    like mice or rats
  • EGGS
    embryonated eggs–sterile, self-sustained
  • TISSUE CULTURE
    primary and a continuous cell line
49
Q

how do we grow BACTERIOPHAGES?

A

use of AGAR MIXTURE and PHAGE DILUTION MIXTURE

  • poured ON TOP OF NUTRIENT AGAR PLATE
  • viruses are now SANDWICHED BETWEEN TOP AGAR and NUTRIENT AGAR
  • is then INCUBATED and creation of PHAGE PLAQUES
50
Q

describe VIROIDS

A
  • NON CAPSID
  • CIRCULAR RNA
  • EXTREMELY SMALL
  • INFECTIOUS PARTICLES
  • FOUND IN PLANTS
51
Q

describe PRIONS

A
  • type of INFECTIOUS PROTEIN
  • seen where a normal cellular protein becomes INFECTIOUS
  • type of GENETIC PREDISPOSITION
52
Q

what disorders can PRIONS cause?

A
  • BSE (MAD COW DISEASE)
  • SCRAPIE

MICROBIO BIOL-160 LEC (21 decks)

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