Block 2 Flashcards
CULTIVATING VIRUSES WHY IS
THERE NO GROWTH?
Can you culture a virus?
what is needed to replicate?
How does it work?
- VIRUSES DON’T HAVE THE GENETIC CAPABILITY TO
MULTIPLY BY DIVISION WITHOUT THE HOST. THIS MEANS
VIROLOGISTS CANNOT CULTURE VIRUSES. - A VIRUS NEEDS THE HOST IN ORDER TO REPLICATE.
- HOW?
- THE VIRUS UTILIZES THE HOST CELLS ORGANELLES TO
PRODUCE ITS PROTEINS AND NUCLEIC ACID FOR
REGENERATION
HOW CAN YOU CULTIVATE VIRUSES?
(3)
- CELL/TISSUE CULTURE
- INOCULATION IN EMBRYONATED EGG
- LABORATORY ANIMALS
WHAT ARE THE KINDS OF CELL CULTURES?
(3)
Suspension culture (not important for us now)
Primary Cell Culture
Monolayer culture
WHAT ARE THE KINDS OF CELL CULTURES?
Primary Cell Culture
what is it?
what is it good for?
what is it used for?
- This is the maintenance of the growth of the cells dissociated DIRECTLY from parental tissues of the
human or animal organ. - These are the best culture systems for isolating viruses and propagating them
- They’re used to make viral vaccines
WHAT ARE THE KINDS OF CELL CULTURES?
Monolayer culture
explain
- This means when the bottom of the culture vessel is completely covered with a continuous layer of
cells typically only one cell thick.
CELL CULTURE
How is this done?
Cell culture refers to the removal of cells from an animal or plant and their subsequent
growth in a favorable artificial environment.
Cell culture involves the growth of dispersed cells in-vitro, either as cells in
suspension, or as a monolayer on a solid surface such as a inner surface of polystyrene
culture flask.
CELL CULTURE
Suspension cultures
what is this?
Suspension cultures- Cells which do not
require attachment for growth or do not
attach to the surface of the culture
vessels. Can be propagated in suspension.
WHAT ARE THE KINDS OF CELL
CULTURES?
SUBCULTURE CELL CULTURES
explain
SUBCULTURE CELL CULTURES: THIS IS THE PASSAGE OF
CELLS FROM ONE CULTURE VESSEL TO ANOTHER IN ORDER
TO OBTAIN ADEQUATE FRESH NUTRIENTS AND SPACE.
* SUBCULTURES ARE REQUIRED FOR DEVELOPING CELL LINES
CELL LINES
what are the 2 kinds?
1-CONTINUOUS CELL LINES/IMMORTAL CELL LINES/HETEROPLOIDY CELL LINES
2-FINITE/DIPLOID CELL LINES
CELL LINES
- CONTINUOUS CELL LINES/IMMORTAL CELL LINES/HETEROPLOIDY CELL LINES
what are these?
what can’t they be used for?
- CONTINUOUS CELL LINES/IMMORTAL CELL LINES/HETEROPLOIDY CELL LINES
- THESE CAN DIVIDE INDEFINITELY AND ARE DERIVED DIRECTLY FROM CANCER CELLS
- THESE CANNOT BE USED FOR VACCINE PRODUCTION AS INDICATED BY THE FDA.
CELL LINES
- FINITE/DIPLOID CELL LINES
what are they?
what can they be used for?
- FINITE/DIPLOID CELL LINES
- CELL LINES THAT HAVE A LIMITED LIFE SPAN AND ARE DERIVED MAINLY FROM EMBRYOS; OR
SECONDARY CELL CULTURES - THE CAN BE USED FOR VACCINE PRODUCTION!
Types of cell cultures
Cell Line
Finite cell lines/Diploid Cell Lines
what kind of population?
what is the life span?
can they be subcultured? how?
where do they come from?
what do they retain ?
what 3 properties do they maintain?
what is the speed of growth?
are they easy or hard to use?
example?
**Homogenous **population of a single cell type – fewer cell types
Limited life span: May be sub-cultured up to 100 times before the cells die
Derived mainly from embryos; or from secondary cell cultures
Cell retains original morphology and diploid chromosome number
These cell lines exhibit the property of contact inhibition, density limitation and
anchorage dependence
The growth rate is slow and doubling time is around 24-96 hours
Technically, less hassle to use
Example: WI-38 (WI: Wistar Institute) is a diploid human cell culture line composed
of fibroblasts derived from lung tissue of a three month old white female fetus.
Types of cell cultures
Cell Line
Continuous cell lines/Immortal Cell Lines/Heteroploid Cell Lines
single or multiple cell type?
where are they derived from? (2)
limited or infinite cell division?
genetically normal or strange? why?
what is missing
speed of growth?
easy or difficult to use?
what are they prohibited from? why?
Cell cultures of a single cell type - Most homogeneous
Derived directly from cancer cells; or induced transformation of a primary or diploid
cell strain to divide indefinitely
Genetically weird – furthest from animal. Abnormal morphology & chromosome
number
Absence of contact inhibition and anchorage dependence
The growth rate is rapid and doubling time can be 12-24 hours
Hassle free to use
FDA prohibits their use in Vaccine Production Bluthey
are
cancerous
cells
Morphology of Cells in Culture
How many catagories?
what is used to catagorize them?
Cells in culture can be divided in to three basic categories based on their shape
and appearance
Morphology of Cells in Culture
what are the 3 catagories?
- Fibroblastic
- Epithelial-like
- Lymphoblast-like
Morphology of Cells in Culture
Fibroblastic
explain
- Fibroblastic (or fibroblast-like) cells are bipolar or
multipolar, have elongated shapes, and grow attached
to a substrate.
Morphology of Cells in Culture
Epithelial-like
explain
Epithelial-like cells are polygonal in shape with
more regular dimensions, and grow attached to a
substrate in discrete patches.
Morphology of Cells in Culture
Lymphoblast-like
explain
Lymphoblast-like cells are spherical in shape
and usually grown in suspension without attaching
to a surface.
CELL CULTURE ENVIRONMENT
CULTURE MEDIUM
what is it?
CULTURE MEDIUM: CONTAINS ALL THE NUTRIENTS REQUIRED FOR THE GROWTH
OF CELLS.
CELL CULTURE ENVIRONMENT
SERUM IN CULTURE MEDIUM
what is the most common?
what 3 things does it help do?
SERUM IN CULTURE MEDIUM:
* FETAL BOVINE SERUM IS THE MOST WIDELY USED SERUM IN CULTURE MEDIA
FOR GROWTH AND MAINTENANCE OF CELLS. IT AIDS IN THE CELL ADHESION,
REGULATION OF CELL MEMBRANE PERMEABILITY AND PROVIDING NUTRIENTS.
CELL CULTURE ENVIRONMENT
PHENOL RED PH INDICATOR
what does red mean
what does orange yellow mean
what does yellow mean
PHENOL RED PH INDICATOR IS THE INDICATION OF PH VIA COLOR CHANGE.
* IF THE SOLUTION IS RED THE PH IS >7 (BASIC)
* IF THE SOLUTION TURNS ORANGE/YELLOW THE PH IS <7 (ACIDIC)
”+” it changes
toyellow (this is your note, but it is too small forme to read. see slide 11)
CELL CULTURE ENVIRONMENT
CO2 LEVEL
relevance?
CO2 LEVEL: ENSURE TO MONITOR THE CO2 LEVEL WHEN USING MEDIA BUFFERED
WITH A CO2-BICARBONATE BASED BUFFER IN ORDER TO MAINTAIN THE PH OF THE
MEDIUM
CELL CULTURE ENVIRONMENT
ANTIMICROBIAL AGENTS
purpose?
ANTIMICROBIAL AGENTS: PREVENTS CONTAMINATION WITH BACTERIA,
MYCOPLASMA, YEAST, MOLDS, ETC
TRYPSIN
what is it? why is it used? what result?
- A PROTEOLYTIC ENZYME USED TO DETACH AND DISSOCIATE CELLS WHILE
SUBCULTURING. WHICH MEANS IT WILL STOP THE CELLS FROM ADHERING TO THE VESSEL.
What would you use to detach and
dissociate cells for subculture?
Trypsin
CYTOPATHIC EFFECT OR CYTOPATHOGENIC EFFECT
(CPE)
explain
THIS REFERS TO THE DAMAGE OR CHANGES THAT OCCUR IN THE HOST CELLS AS A
CONSEQUENCE OF VIRAL INVASION
WHAT ARE THE ROUTES OF EGG INOCULATION?
(4)
- YOLK SAC INOCULATION
- ALLANTOIC CAVITY INOCULATION
- AMNIOTIC CAVITY INOCULATION
- CHORIOALLANTOIC MEMBRANE INOCULATION
WHAT INDICATED VIRUS GROWTH IN THE EGG?
(4)
- DEATH OF THE EMBRYO
- PARALYSIS OR SLOW MOVEMENT
- STUNTED GROWTH
- POCKS ON THE CHORIOALLANTOIC MEMBRANE (CAM)
Evidence of Virus Growth
(7)
- Death of the embryo
- Paralysis [sluggish movement]
- Stunted growth
- Urate deposits in the mesonephros
- Hemorrhage and congestion
- Hemagglutins in embryonic fluids
- Extracellular membrane lesions
Which one of the following is not a common
method of virus inoculation in embryonated
eggs?
A.Yolk Sac Inoculation
B.Chorioallantoic Membrane Inoculation
C.Amniotic Cavity Inoculation
D.Air Sac inoculation
Which one of the following is not a common
method of virus inoculation in embryonated
eggs?
A.Yolk Sac Inoculation
B.Chorioallantoic Membrane Inoculation
C.Amniotic Cavity Inoculation
D.Air Sac inoculation ×
PURIFICATION AND CONCENTRATION
ULTRACENTRIFUGE
what is it wha tis it used for?
ULTRACENTRIFUGE: EFFICIENTLY SEDIMENTS EVEN THE SMALLEST VIRUSES
THOUGH THEY MAY NEED TO BE SPUN FOR AWHILE IF THEY ARE VERY SMALL
VIRUSES. THESE ARE USED FOR CONCENTRATION AND PURIFICATION OF
VIRUSES.
PURIFICATION AND CONCENTRATION
RATE-ZONAL CENTRIFUGATION
what is this?
RATE-ZONAL CENTRIFUGATION: RATE OF MOVEMENT IS DEPENDENT UPON
THE MASS OF THE PARTICLE.
PURIFICATION AND CONCENTRATION
ISOPYNCNIC CENTRIFUGATION
what is this
what is another name
what is the basis of seperation
ISOPYNCNIC CENTRIFUGATION (BUOYANT SEPARATION/EQUILIBRIUM
SEPARATION): SEPARATION SOLELY ON THE BASIS OF THEIR BUOYANT
DENSITY. (PARTICLES WILL NEVER FORM A SEDIMENT NO MATTER HOW MUCH
IT’S SPUN.
PURIFICATION AND CONCENTRATION
Name 4
ULTRACENTRIFUGE
RATE-ZONAL CENTRIFUGATION
ISOPYNCNIC CENTRIFUGATION
VIRUS PURIFICATION WITH MEMBRANE CHROMATOGRAPHY
In rate-zonal centrifugation, virus particles are separated on
basis of their buoyant density.
true or false?
False
seperated on basis of mass
QUANTIFICATION OF VIRUSES
what is it?
what is a virus titer?
- VIRUS QUANTIFICATION: THE NUMBER OF VIRUSES IN A SPECIFIC VOLUME IN ORDER TO
DETERMINE THE VIRUS CONCENTRATION. - VIRUS TITER: THE LOWEST CONCENTRATION OF THE VIRUS NEEDED TO INFECT THE CELLS.
(INFECTIOUS UNITS PER ML OF SAMPLE).
TESTS FOR VIRUS QUANTIFICATION
what are the 2?
BIOLOGICAL TESTS
PHYSICAL TESTS
TESTS FOR VIRUS QUANTIFICATION
BIOLOGICAL TESTS
what do they depend on?
vs
PHYSICAL TESTS
what do they depend on?
**Know the differences
BIOLOGICAL TESTS
* THE BIOLOGICAL TEST WILL DEPEND ON
THE VIRUSES ABILITY TO MULTIPLY
* PLAQUE ASSAYS
* POCK ASSAYS
* VARIOUS ENDPOINT TITRATION METHODS
vs.
PHYSICAL TESTS
* DOES NOT RELY ON THE VIRUS TO
MULTIPLY
* ELECTRON MICROSCOPIC PARTICLE
COUNTS
* HEMAGGLUTINATION
* IMMUNOLOGICAL ASSAYS SUCH AS ELISA
* QUANTITATIVE PCR ASSAYS
* FLOW CYTOMETRY
PHYSICAL TESTS
what 3 ways
- DIRECT COUNTING OF VIRAL PARTICLES IN SOLUTION
- ASSESSMENT BASED ON ANTIGEN CONCENTRATION
- ASSESSMENT BASED ON GENE EXPRESSION
PHYSICAL TESTS
- DIRECT COUNTING OF VIRAL PARTICLES IN SOLUTION
explain
- DIRECT COUNTING OF VIRAL PARTICLES IN SOLUTION
- TRANSMISSION ELECTRON MICROSCOPY (TEM): THIS IS THE MOST DIRECT METHOD TO DETERMINE THE
CONCENTRATION OF VIRUS PARTICLES - VIRUS COUNTER 2100
PHYSICAL TESTS
- ASSESSMENT BASED ON ANTIGEN CONCENTRATION
explain
- ASSESSMENT BASED ON ANTIGEN CONCENTRATION
- HEMAGGLUTINATION ASSAY (SOME VIRUSES CLUMP IN ASSAY)
- SINGLE RADIAL IMMUNODIFFUSION (SRID). INCREASE ANTIGEN, INCREASE THE VIRUS
PHYSICAL TESTS
- ASSESSMENT BASED ON GENE EXPRESSION
explain
- ASSESSMENT BASED ON GENE EXPRESSION
- QUANTITATIVE POLYMERASE CHAIN REACTION
BIOLOGICAL ASSAYS (TRADITIONAL ASSAYS)
name 3
- MONOLAYER PLAQUE ASSAY
- POCK ASSAYS: NECROTIC AREA ON CHORIOALLANTOIC MEMBRANE (CAM) OF AN
EMBRYONATED EGG - TRANSFORMATION ASSAY:
BIOLOGICAL ASSAYS (TRADITIONAL ASSAYS)
* MONOLAYER PLAQUE ASSAY
explain
- PLAQUE: A CIRCULAR ZONE OF NECROTIC CELLS SURROUNDED BY VIABLE CELLS IN A
MONOLAYER - UNITS: PLAQUE FORMING UNITS (PFU). EXAMPLE: IF A SOLUTION HAS A PFU OF 50, THIS MEANS
QA THERE ENOUGH VIRUS IN 1 ML OF SOLUTION TO FORM 50 PLAQUES.
BIOLOGICAL ASSAYS (TRADITIONAL ASSAYS)
* POCK ASSAYS: NECROTIC AREA ON CHORIOALLANTOIC MEMBRANE (CAM) OF AN
EMBRYONATED EGG
explain
- POCK ASSAYS: NECROTIC AREA ON CHORIOALLANTOIC MEMBRANE (CAM) OF AN
EMBRYONATED EGG - UNIT: POCK-FORMING UNITS/ML
BIOLOGICAL ASSAYS (TRADITIONAL ASSAYS)
TRANSFORMATION ASSAY
explain
TRANSFORMATION ASSAY: THE QUANTITATIVE DETERMINATION OF TITERS OF ONCOGENIC
VIRUSES. ONCOGENIC VIRUSES WILL TRANSFORM THE CELLS AND MAKE THEM LOSE
CONTACT INHIBITION (START PILING UP ON EACH OTHER).
* UNIT: FOCUS-FORMING UNITS/ML
QUANTAL ASSAYS
* END POINT
explain
- END POINT: VIRUS DILUTION THAT AFFECTS 50% OF THE TEST SUBJECTS.
- TDCID50 IS THE TISSUE CULTURE INFECTIOUS DOSE WHICH WILL INFECT 50% OF THE CELL
MONOLAYERS INOCULATED.
! Which of the following is not a physical
assay for quantification of viruses?
A. Electron Microscopy
B. ELISA
C. Pock Assay
D. qPCR
! Which of the following is not a physical
assay for quantification of viruses?
A. Electron Microscopy
B. ELISA
C. Pock assay
D. qPCR
A PFU/ml of 300 means ____
A. 300 viruses are present in 1 ml of sample to cause one
plaque in monolayer cell culture.
B. One virus is present per ml of sample to form 300
plaques in monolayer cell culture.
C. The minimum # of viruses present per ml of the Osample to form 300 plaques in monolayer cell culture.
C. The minimum # of viruses present per ml of the Osample to form 300 plaques in monolayer cell culture.
VIRUS REPLICATION
how?
Name 4 ways
VIRUSES DON’T HAVE THE GENETIC CAPABILITY TO REPLICATE ON THEIR OWN. THE VIRUS MUST HIJACK THE HOST CELL IN ORDER TO
PRODUCE ITS PROTEINS AND NUCLEIC ACID NECESSARY FOR REPLICATION. THE PROCESS OF REPLICATION RESEMBLES AN ASSEMBLY
LINE.
- PERMISSIVE CELL
- NON-PERMISSIVE CELL
- MOI (MULTIPLICITY OF INFECTIONS)
- CO-RECEPTOR
VIRUS REPLICATION
- PERMISSIVE CELL
what is it?
- PERMISSIVE CELL: A CELL IN WHICH THE MACHINERY SUPPORTS THE VIRUS IN REPLICATION
VIRUS REPLICATION
* NON-PERMISSIVE CELL
what is it?
- NON-PERMISSIVE CELL: A CELL THAT DOES NOT HAVE ONE OR MORE FACTORS IN WHICH THE VIRUS NEEDS TO REPLICATE . I.E. THE
ABSENCE OF APPROPRIATE RECEPTORS.
VIRUS REPLICATION
* MOI (MULTIPLICITY OF INFECTIONS)
what is it?
- MOI (MULTIPLICITY OF INFECTIONS): THE NUMBER OF VIRIONS THAT ARE ADDED PER CELL DURING THE INFECTION
VIRUS REPLICATION
* CO-RECEPTOR
what is it?
- CO-RECEPTOR SOMETIMES AN ADDITIONAL CELL SURFACE MOLECULE IS REQUIRED FOR ENTRY INTO CELL.
ONE STEP VIRUS GROWTH CURVE
what happens
relevance of absorption?
ECLIPSE PERIOD: THE TIME INTERVAL BETWEEN UNCOATING AND APPEARANCE,
INTRACELLULARLY, OF THE FIRST INFECTIOUS PROGENY VIRIONS
* LATENT PERIOD: THE TIME FROM UNCOATING TO JUST PRIOR TO THE RELEASE OF THE FIRST
EXTRACELLULAR VIRIONS. NO EXTRACELLULAR VIRIONS ARE DETECTED IN THIS STAGE.
* BURST SIZE: THE NUMBER OF INFECTIOUS VIRIONS RELEASED PER AVERAGE CELL.
Absorption: during this period, virus ataches to and enters cells, and the titer of gree virus in the medium may actually decline.
ATTACHMENT TO THE HOST CELL
specific or general?
how are they mediated?
is binding sufficient?
how many host cell receptors are needed?
- VIRUS ATTACHMENT TO RECEPTOR/S ON HOST CELLS ARE VERY
SPECIFIC (LIKE LOCK AND KEY) EACH VIRUS HAS ITS OWN SPECIFIC
RECEPTOR ON SPECIFIC HOST CELLS. - THESE INTERACTIONS ARE MEDIATED BETWEEN THE VIRUS AND
COMPLIMENTARY RECEPTOR ON THE HOST SURFACE. CELLS THAT
DON’T HAVE THE RECEPTOR, WON’T BE INFECTED BY THE VIRUS. - IN SOME CASES, BINDING TO A CELLULAR RECEPTOR IS NOT
SUFFICIENT FOR INFECTION. AN ADDITIONAL CELL SURFACE
MOLECULE OR A CO-RECEPTOR MUST BE USED FOR ENTRY SUCH AS
HIV WHO USES MORE THAN ONE HOST CELL RECEPTOR. - SOME VIRUSES CAN USE MORE THAN ONE HOST CELL RECEPTOR
(LIKE HIV)
VIRUS PENETRATION AND UNCOATING IN THE HOST
CELL
2 kinds what are they?
explain
NONENVELOPED/NAKED
VIRUSES
- RECEPTOR MEDIATED ENDOCYTOSIS
(COMMONLY SEEN) - PORE MEDIATED PENETRATION (IN SOME
NAKED VIRUSES)
vs.
ENVELOPED VIRUSES
- SURFACE MEMBRANE FUSION (HAVE A PH
INDEPENDENT FUSION PROTEIN) - RECEPTOR MEDIATED ENDOCYTOSIS (HAVE
A PH DEPENDENT FUSION PROTEIN)
NON-ENVELOPED VIRUSES
what happens in many?
what happens in some?
* IN MANY: CLATHRIN-MEDIATED ENDOCYTOSIS OR ANY OTHER RECEPTOR MEDIATED ENDOCYTOSIS OF VIRUS BY
HOST.
* IN SOME: PORE MEDIATED PENETRATION OF VIRAL GENOME INTO THE HOST CELL. SOME NON-ENVELOPED VIRUSES
INJECT THEIR GENOME INTO THE HOST CYTOPLASM THROUGH CREATION OF A PORE IN THE HOST MEMBRANE.
ENVELOPED VIRUSES
Name 2
- SURFACE MEMBRANE FUSION (HAVE PH INDEPENDENT FUSION PROTEIN).
- RECEPTOR MEDIATED ENDOCYTOSIS (HAVE PH DEPENDENT FUSION PROTEIN).
ENVELOPED VIRUSES
* SURFACE MEMBRANE FUSION (HAVE PH INDEPENDENT FUSION PROTEIN).
explain
- SURFACE MEMBRANE FUSION (HAVE PH INDEPENDENT FUSION PROTEIN). THE FUSION
OCCURS DIRECTLY ON THE SURFACE OF A HOST CELL FACILITATED BY PH INDEPENDENT FUSION
PROTEINS.
ENVELOPED VIRUSES
* RECEPTOR MEDIATED ENDOCYTOSIS (HAVE PH DEPENDENT FUSION PROTEIN).
explain
RECEPTOR MEDIATED ENDOCYTOSIS (HAVE PH DEPENDENT FUSION PROTEIN). HERE THE
FUSION REQUIRES A LOW PH TO GET ACTIVATED-THIS IS ACHIEVED VIA AN ENDOSOME
FACILITATING THE VIRUS ENVELOPE FUSION WITH ENDOSOMAL MEMBRANE.
OTHER: ANTIBODY MEDIATED ATTACHMENT AND
PENETRATION
explain
example
- ANTIBODIES AGAINST THE VIRUS BINDS AND FACILITATES ENTRY THROUGH THE IGG-FCY
RECEPTOR. - EXAMPLE: FIP VIRUS
! Which one of the following methods cannot be used by
viruses for penetrating into host cell?
A. Receptor-mediated endocytosis
B. Membrane fusion
C. Pore-mediated penetration
D. Exocytosis
D. Exocytosis
VIRUS UNCOATING
what is it?
what happens?
what result?
- RELEASE OF VIRAL GENOME IN HOST CELL.
- VIRION CAN NO LONGER BE DETECTED.
- LOSS OF INFECTIVITY OF VIRIONS
- FUNCTIONS OF THE PARENT VIRUS:
- MULTIPLE COPIES FOR NEW VIRUSES (CHILDREN/PROGENY).
- VIRAL PROTEINS FOR CAPSID AND SUCCESSFUL REPLICATION.
REVERSE TRANSCRIPTASE
what is it?
explain
- RNA-DEPENDENT DNA POLYMERASE & ALSO HAS DNA-DEPENDENT DNA POLYMERASE
ACTIVITY.
* CONVERSION OF VIRAL RNA TO CDNA DURING VIRUS REPLICATION
Q
PROCESSING OF PRIMARY RNA TRANSCRIPT (PRE-
MRNA)
what is it?
what happens?
- THE VIRAL MRNA MUST BE RECOGNIZED BY THE HOST CELL VIA:
- CAPPING
- ADDITION OF POLYA TAIL
- SPLICING
STEPS OF PRIMARY RNA TRANSCRIPT
what are the 3 steps?
what happens in the steps?
First: Capping:-Addition of 7-methylguanosine to the 5’ end of RNA
Second: Addition of 3’ poly-adenylated tailsThe poly-taa tail is added to the viral mRNA
Third: Splicing-RNA splicing is a process that removes introns and joins
exons in a primary transcript.
STEPS OF PRIMARY RNA TRANSCRIPT
what is an exon?
an eson is the portion of a gene that codes for amino acids
STEPS OF PRIMARY RNA TRANSCRIPT
what is an intron?
the portion of a gene that does not code for amino acids
STEPS OF PRIMARY RNA TRANSCRIPT
what is alternative splicing? what result?
all interons spliced out; only selected exons spliced in. result: mRNAs having different coding informaion derived from a single gene
The poly-A tail is added to the 3’-end of viral mRNA?
true/false
false
Types of Viral mRNA (2)
what are they how are they different?
Monocistronic
mRNA that encodes** one** polypeptide
* Polycistronic
!mRNA that encodes several polypeptides
ASSEMBLY AND MATURATION
is there a specific order?
how are they packaged?
where does it occur?
- ASSEMBLY OF VIRUS GENOME AND PROTEINS FOLLOW A SPECIFIC ORDER
- THEY ARE ALL PACKAGED TO FORM MATURE VIRIONS
- TAKES PLACE IN THE NUCLEUS, CYTOPLASM, PLASMA/CELL MEMBRANE (MOST ENVELOPED
VIRUSES)
RELEASE OF PROGENY VIRIONS
how does this occur with naked virons?
how does this occur iwth envoloped virons?
- NAKED VIRIONS
- LYSIS OF THE HOST CELL
- CANNOT EXIT THE HOST CELL BY BUDDING AS THEY LACK AN ENVELOPE
- ENVELOPED VIRIONS
- BUDDING
EXOCYTOSIS
what is it?
VIRUSES THAT ACQUIRE THE ENVELOPE WHILE
BUDDING FROM THE ER, GOLGI OR NUCLEAR
MEMBRANE ARE RELEASED FROM THE INFECTED
HOST CELL VIA EXOCYTOSIS
Viruses can acquire the lipid envelope only from the
cell membrane of infected host cells.
A. True
B. False
B. False
REPLICATION OF RETROVIRUSES
2 ways what are they, how do they work?
- REVERSE TRANSCRIPTASE: VIRAL RNA TO DNA
- INTEGRASE: INTEGRATES VIRAL DNA INTO HOST
GENOME
CELL TO CELL SPREAD OF VIRUSES
3 ways-what are they?
- EXTRACELLULAR SPREAD
- INTERCELLULAR SPREAD
- NUCLEAR SPREAD OF VIRUS GENOME (RETROVIRUS)
