Virology Exam 1 (Columbia - Racaniello)
UPDATED ACTUAL Exam Questions and
CORRECT ANSWERS
1. How many viruses do we carry at any given time? Why don't these make us sick? -
CORRECT ANSWER- ✔✔- most viruses just pass through us
- non-human viruses
- Viruses can be beneficial (thermotolerant fungi)
- Strong immune system!
How can viruses be beneficial? Why do we care that they comprise the most biodiversity on
the planet? - CORRECT ANSWER- ✔✔Co-evolution, thermotolerant fungi, enteric virus
replaces function of commensal bacteria
What is a virus? - CORRECT ANSWER- ✔✔An infectious, obligate intracellular parasite
comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane
Viroid - CORRECT ANSWER- ✔✔just infect plants, naked RNA (ancient virus?)
Virion - CORRECT ANSWER- ✔✔infectious viral particle
How does viral replication differ from that of bacteria? - CORRECT ANSWER- ✔✔Viruses
must assemble using pre-formed components!
No binary fission/splitting.
Make the parts and then assemble the product (eclipse period --> burst/yield).
Bacteria grow immediately in media at a logarithmic rate. Viruses have very different growth
curve.
Eclipse Period - CORRECT ANSWER- ✔✔Virions penetrate the cells. No virus detectable.
,Burst/Yield - CORRECT ANSWER- ✔✔Host cells release many viral particles.
Tobacco Mosaic Disease - CORRECT ANSWER- ✔✔First virus!
Virus discovery - filterable agents. What was on the filter did not cause the disease, but what
went through the filter caused disease. Must have been something very small.
Why was filtration used to define viruses, and how has this parameter changed? - CORRECT
ANSWER- ✔✔What was on the filter did not cause the disease, but what went through the
filter caused disease. Must have been something very small. Originally thought it was a
poisonous liquid.
Virus Classification - CORRECT ANSWER- ✔✔1. Nature and sequence of nucleic acid in
virion
2. Symmetry of protein shell (capsid)
3. Presence or absence of lipid membrane (envelope)
4. Dimensions of virion and capsid
Virus growth curve - CORRECT ANSWER- ✔✔
Virus titer aka Viral load - CORRECT ANSWER- ✔✔numerical expression of the quantity of
virus in a given volume
higher viral burden, titre, or viral load often correlates with the severity of an active viral
infection
Why do we care about viruses? - CORRECT ANSWER- ✔✔1. Greatest biodiversity on
Earthy --> enormous genetic diversity and variation, can transfer to host cells via horizontal
gene transfer
2. Drive Global Cycles - carbon, etc.
3. Beneficial
, 4. Sources of new pathogens - can always jump into people
How does the discovery of new viruses today differ from 100 years ago? - CORRECT
ANSWER- ✔✔Disease driven vs. Curiosity driven
What two simple facts provide an underlying simplicity and order to viruses? - CORRECT
ANSWER- ✔✔1. All viral genomes are obligate molecular parasites that can only function
after they replicate in a cell
2. All viruses must make mRNA that can be translated by host ribosomes - they are all
parasites of the host protein synthesis machinery.
Susceptible Cell - CORRECT ANSWER- ✔✔cell has functional receptor for a given virus -
may or may not be able to support viral replication
Permissive Cell - CORRECT ANSWER- ✔✔cell has capacity to replicate virus - may or may
not be susceptible
Resistant Cell - CORRECT ANSWER- ✔✔No receptor - may or may not be competent to
support viral replication
Cytopathic Effect - CORRECT ANSWER- ✔✔structural changes in host cells that are caused
by viral invasion. infecting virus causes lysis of the host cell or when the cell dies without
lysis due to an inability to reproduce.
*Very large diversity of CPEs!
Common CPEs:
- rounding of infected cell
- Syncytia - fusion with adjacent cells
- Inclusion bodies (ie protein aggregates)
UPDATED ACTUAL Exam Questions and
CORRECT ANSWERS
1. How many viruses do we carry at any given time? Why don't these make us sick? -
CORRECT ANSWER- ✔✔- most viruses just pass through us
- non-human viruses
- Viruses can be beneficial (thermotolerant fungi)
- Strong immune system!
How can viruses be beneficial? Why do we care that they comprise the most biodiversity on
the planet? - CORRECT ANSWER- ✔✔Co-evolution, thermotolerant fungi, enteric virus
replaces function of commensal bacteria
What is a virus? - CORRECT ANSWER- ✔✔An infectious, obligate intracellular parasite
comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane
Viroid - CORRECT ANSWER- ✔✔just infect plants, naked RNA (ancient virus?)
Virion - CORRECT ANSWER- ✔✔infectious viral particle
How does viral replication differ from that of bacteria? - CORRECT ANSWER- ✔✔Viruses
must assemble using pre-formed components!
No binary fission/splitting.
Make the parts and then assemble the product (eclipse period --> burst/yield).
Bacteria grow immediately in media at a logarithmic rate. Viruses have very different growth
curve.
Eclipse Period - CORRECT ANSWER- ✔✔Virions penetrate the cells. No virus detectable.
,Burst/Yield - CORRECT ANSWER- ✔✔Host cells release many viral particles.
Tobacco Mosaic Disease - CORRECT ANSWER- ✔✔First virus!
Virus discovery - filterable agents. What was on the filter did not cause the disease, but what
went through the filter caused disease. Must have been something very small.
Why was filtration used to define viruses, and how has this parameter changed? - CORRECT
ANSWER- ✔✔What was on the filter did not cause the disease, but what went through the
filter caused disease. Must have been something very small. Originally thought it was a
poisonous liquid.
Virus Classification - CORRECT ANSWER- ✔✔1. Nature and sequence of nucleic acid in
virion
2. Symmetry of protein shell (capsid)
3. Presence or absence of lipid membrane (envelope)
4. Dimensions of virion and capsid
Virus growth curve - CORRECT ANSWER- ✔✔
Virus titer aka Viral load - CORRECT ANSWER- ✔✔numerical expression of the quantity of
virus in a given volume
higher viral burden, titre, or viral load often correlates with the severity of an active viral
infection
Why do we care about viruses? - CORRECT ANSWER- ✔✔1. Greatest biodiversity on
Earthy --> enormous genetic diversity and variation, can transfer to host cells via horizontal
gene transfer
2. Drive Global Cycles - carbon, etc.
3. Beneficial
, 4. Sources of new pathogens - can always jump into people
How does the discovery of new viruses today differ from 100 years ago? - CORRECT
ANSWER- ✔✔Disease driven vs. Curiosity driven
What two simple facts provide an underlying simplicity and order to viruses? - CORRECT
ANSWER- ✔✔1. All viral genomes are obligate molecular parasites that can only function
after they replicate in a cell
2. All viruses must make mRNA that can be translated by host ribosomes - they are all
parasites of the host protein synthesis machinery.
Susceptible Cell - CORRECT ANSWER- ✔✔cell has functional receptor for a given virus -
may or may not be able to support viral replication
Permissive Cell - CORRECT ANSWER- ✔✔cell has capacity to replicate virus - may or may
not be susceptible
Resistant Cell - CORRECT ANSWER- ✔✔No receptor - may or may not be competent to
support viral replication
Cytopathic Effect - CORRECT ANSWER- ✔✔structural changes in host cells that are caused
by viral invasion. infecting virus causes lysis of the host cell or when the cell dies without
lysis due to an inability to reproduce.
*Very large diversity of CPEs!
Common CPEs:
- rounding of infected cell
- Syncytia - fusion with adjacent cells
- Inclusion bodies (ie protein aggregates)
