Viruses Flashcards
describe the DEFINITION OF LIFE and how VIRUSES play into said definition?
- 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
definition of VIRUSES
- 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
what do VIRUSES NOT DO? (7)
- 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
the more PROPER DEFINITION OF A VIRUS
- 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
describe the TYPICAL VIRUS and its INTRACELLULAR/EXTRACELLULAR STATES
- 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
describe the CHARACTERISTICS OF EXTRACELLULAR (VIRION) and INTRACELLULAR (VIRUS)
VIRION
- has a PROTEIN COAT (CAPSID)
- has RECOGNITION for HOST
- can have a PHOSPHOLIPID COVER (ENVELOPE)
VIRUS
- NO CAPSID PRESENT
- has REPLICATION STAGE
describe a VIRUS GENOME SIZE
- E. Coli GENOME around 4.5 - 5.5 million BP
- VIRUSES around 30,000 - 300,000 BP
describe the VIRAL GENOME
- 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
describe DNA VIRUSES
- they are NON-SEGMENTED (all in ONE PIECE)
- can be LINEAR or CIRCULAR
- can be ds or ss
describe RNA VIRUSES
- can be NON SEGMENTED or SEGMENTED
- can be LINEAR or CIRCULAR
- can be ds or ss
- if SS; can be either - or + sense
describe RNA VIRUSES – (-) or (+) SENSE
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
describe VIRAL SIZE
- can be only up to 10 nm to 400 nm
(nm - 10^-9 meter)
describe CAPSID and their function
- has REPETITIVE UNITS of ONE OR FEW PROTEINS that are known as CAPSOMERES
FUNCTIONS:
- PROTECTION
- ATTACHMENT and PENETRATION of HOST CELL
describe VIRAL MORPHOLOGY
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
describe a VIRUS ENVELOPE
- 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
what can VIRUSES INFECT?
- 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
how are VIRUSES CLASSIFIED/
- based on the SYMPTOMS OF DISEASES caused by the VIRUS
- use of INTERNAL COMMITTEE on TAXONOMY OF VIRUSES (ICTV)
- based on genomics and structure
definition of VIRAL SPECIES
- a GROUP OF VIRUSES that SHARE THE SAME GENETIC INFORMATION and HOST RANGE
describe the BASIC STAGES of VIRAL REPLICATION
- ATTACHMENT
locate and stick - ENTRY
getting in - SYNTHESIS
making pieces - ASSEMBLY
putting it together - LYSIS
getting out
what are the FIVE STEPS of the LYTIC CYCLE
- ATTACHMENT
- ENTRY
- SYNTHESIS
- ASSEMBLY
- LYSIS
describe ATTACHMENT (1) of the LYTIC CYCLE
- 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)
describe ENTRY (2) of the LYTIC CYCLE
- 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
describe SYNTHESIS and ASSEMBLY (3-4) of LYTIC CYCLE
- 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
describe RELEASE (5) of the LYTIC CYCLE
- CELL NOW LYSES and NEW VIRONS ARE RELEASED
- can also be EATEN
definition of BURST TIME and BURST SIZE
BURST TIME:
- the time from attachment to release
- the amount of time of replication
BURST SIZE
- amount of quantity
describe the BASIC STEPS OF LYSOGENIC REPLICATION
- ATTACHMENT
- ENTRY
describe LYSOGENY and LYSOGENIC CYCLE IN GENERAL
- 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
definition of INDUCTION
occasional environmental factors that begin to TRIGGER THE EXCISION of DNA and START A LYTIC CYCLE
what are the THREE IMPORTANT CONSEQUENCES of LYSOGENY?
- HOST IS IMMUNE TO REINFECTION BY SAME VIRUS
- PHAGE CONVERSION–host cell can have new properties such as picking up TOXIN GENES on PROPHAGE
- TRANSDUCTION–the TRANSFER OF BACTERIAL GENES from ONE BACTERIA TO ANOTHER
briefly describe LYSOGENIC CYCLE
- Phage attachment and injection of DNA
- Phage DNA turns CIRCULAR
- begins to INTEGRATE INTO BACTERIAL CHROMOSOME–prophage (by RECOMBINATION)
- continuation of NORMAL BACTERIAL REPRODUCTION with the PHAGE DNA ALREADY INTEGRATED
- will be OCCASIONALLY ACTIVIATED by either INDUCTION or triggering event etc…
describe TRANSDUCTION
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
describe ANIMAL VIRUSES–ATTACHMENT and ENTRY
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
describe ENTRY METHODS of ANIMAL VIRUSES
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
describe SYNTEHSIS within the LYSOGENIC CYCLE
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
what are the TYPES OF GENETIC MATERIAL USED within ANIMAL VIRUSES
- GENETIC MATERIAL can be COPIED AND ADAPTED
GENETIC MATERIAL:
- ds DNA
- ss DNA
- ssRNA (+) or - antisense
- ds RNA
briefly describe the CENTRAL DOGMA
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
describe REPLICATION of a DNA CONTAINING ANIMAL VIRUS
- 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
describe VIRAL GENOME REPLICATION: (+) ssRNA VIRUS and (-) ssRNA VIRUS
(+) 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
why is RdRp so important?
**RdRp really important because PROKARYOTES and EUKARYOTES CANNOT COPY from RNA to RNA
describe VIRAL GENOME REPLICATION: ds RNA VIRUS
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
describe RETROVIRUSES
- 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
describe ASSEMBLY and RELEASE of ANIMAL VIRUSES
- have similar assembly methods–either NUCLEAR or CYTOSOLIC
RELEASE:
- either by BUDDING (with or without an envelope)
- or LYSIS/LYTIC CYCLE
definition of LATENCY and consequences of PROVIRUSES
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
what is CANCER caused by?
- abnormal CELL DIVISION
- often due to VIRAL LYSOGENY/LATENCY
definition of ONCOGENES
genes whose disruption causes cancer
- CHEMICALS
- RADIATION
- VIRUSES
definition of ONCOGENIC VIRUSES
viruses that can INDUCE TUMORS
- can have IRREGULAR SHAPE, ANTIGENS, and CHROMOSOMAL ABNORMALITIES
what are some ONCOGENIC VIRUSES?
Cervical cancer – HPV
Head and neck cancer – HPV
Liver cancer – Hepatitis B
T cell Leukemia – HTLV
Lymphoma - EBV, HIV
how do we GROW VIRUSES?
- MATURE ORGANISMS
like mice or rats - EGGS
embryonated eggs–sterile, self-sustained - TISSUE CULTURE
primary and a continuous cell line
how do we grow BACTERIOPHAGES?
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
describe VIROIDS
- NON CAPSID
- CIRCULAR RNA
- EXTREMELY SMALL
- INFECTIOUS PARTICLES
- FOUND IN PLANTS
describe PRIONS
- type of INFECTIOUS PROTEIN
- seen where a normal cellular protein becomes INFECTIOUS
- type of GENETIC PREDISPOSITION
what disorders can PRIONS cause?
- BSE (MAD COW DISEASE)
- SCRAPIE
