general properties of viruses & 2 general replication strategies

Question 1

virion state

Answer 1

extracellular state of a virus; inert

capable of infecting a host cell

Question 2

are obligate intracellular parasites

Answer 2

cannot reproduce independent of living host cells

Question 3

have a limited host range

Answer 3

can be a single species ex human or bacteria

can even be specific tissue of a wider host range eg white blood cells of mammals

Question 4

host cell receptor

Answer 4

actual host range is determined by a specific host attachment sites

Question 5

basic structure

Answer 5

genome (DNA or RNA)

capsid (protein coat)
made of individual proteins called capsomeres

nucleocapsid= capsid and genome

Question 6

some viruses remain naked outside of their host

Answer 6

exist as a nucleocapsid

Question 7

some viruses are enveloped and have a phospholipid bilayer is external to the nucleocapsid

Answer 7

envelopes are acquired from host cell membranes as a enveloped virus exits the host

Question 8

naked viruses may or may not have

Answer 8

peplomer proteins (aka spikes) on their capsids

Question 9

peplomer proteins are responsible for

Answer 9

host specificity and allow a virion to attach itself to the host cell and initiate infection

some peplomers have additional virulence functions

Question 10

acquisition of envelopes: budding

Answer 10

comes from host cell plasma membrane

camoflage situation

wraps itself around host plasma membrane

Question 11

viruses come in many different

Answer 11

shapes and sizes

Question 12

virus morphologies

Answer 12

icosahedral capsid symmetry
helical capsid symmetry

Question 13

complex capsid

Answer 13

greatly varied structural forms that have additional structures beyond structures beyond the capsid and envelope

ex bacteriophage with tail fibers and pins

Question 14

viral genome diversity

Answer 14

have capsid
genetic info either RNA or DNA

Question 15

envelope can make it appear there is not a

Answer 15

shape

Question 16

virus morphology and arrangement is about

Answer 16

capsid

Question 17

major system for classification of viruses into taxons

Answer 17

baltimore system

Question 18

how many classes are in the baltimore system

Answer 18

7 classes

Question 19

baltimore system is based on

Answer 19

RNA or DNA
single stranded or double stranded

Question 20

2 viral replication strategies

Answer 20

lytic replication

lysogenic replication

Question 21

2 viral replication strategies

Answer 21

lytic replication

lysogenic replicationl

Question 22

lytic replication

Answer 22

“hostile takeover”
host cell bursting (lysis) to release virions and kill the host cell

infection produces LOTS of new virus particles

caused by virulent (aka lytic) viruses and phages

Question 23

lytic replication dsDNA phage

5 steps

Answer 23

1. attachment
   phage attaches by tail fibers (spike fibers) to host bacterium’s cell wall receptors
2. penetration
   phage lysozyme on tail pins open cell wall; tail sheath contracts to force phage DNA into cell
3. Biosynthesis
   production of phage DNA and phage proteins
4. Maturation
   assembly of phage particles

5.Release
phage’s lysozyme breaks cell wall, lysis of cell

Question 24

lysogenic replication

Answer 24

initially “hostile takeover” dormant, reimerges

lysogeny: virus genome incorporates into host genome

prophage/provirus: integrated virus into host genome

infection produces a COPY of viral genome in ever daughter cell but does not kill host cell and DOES NOT produce new virions

caused by temperate (aka lysogenic) viruses and phages

can be triggered to turin into a lytic replication strategy

Question 25

lytic replication

Bio sythesis 3 stages

Answer 25

1st. early mRNA/proteins synthesized

makes a nuclease that degrades host cell’s chromosomes

2nd phage DNA is replicated by phage’s DNA polymerase

3rd late mRNA/proteins are synthesized

Question 26

lysogenic replication

Answer 26

virus attaches and penetrates

virus DNA integrates with (host cell) bacterial chromosome by reccombination and then goes dormant

Question 27

lytic replication animal virus

Answer 27

budding

penetration: membrane fusion, endocytosis, or combination of both

does not break cell wall

Question 28

lytic replication bacteria virus

Answer 28

burst

penetration injects genetic info: break cell wall

Question 29

membrane fusion

Answer 29

peplomers on the virus bind to the host cell receptors on the membrane to facillate virus attachment and maintain host specifity

Question 30

endocytosis

Answer 30

aka pinocytosis

can occur with naked or enveloped virus

genome must be uncoated

peplomers on the virus bind to the host cell receptors on the membrane to facillate virus attachment and maintain host specifity

once the first set of peplomers and receptors bind more sets are in proximity so they also bind until the hosts cells is wrapping its membrane around the virus to produce an endosome

Question 31

endocytosis and membrane fusion

Answer 31

virus attachment and host specificity are maintained by peplomers like in membrane fusion entry

once the first set of peplomers and receptors bind the process continues until the entire virus including the envelope is inside an endosome in the host cytoplasm

the viral envelope fuses with the membrane of the endosome to release the nucleocapsid