©SIRJOEL EXAM SOLUTIONS
10/7/2024 11:03AM
Virology Exam 1 (Columbia - Racaniello)
Questions With Correct Answers
1. How many viruses do we carry at any given time? Why don't these make us sick? - 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? - answer✔Co-evolution, thermotolerant fungi, enteric virus replaces function of
commensal bacteria
What is a virus? - answer✔An infectious, obligate intracellular parasite comprising genetic
material (DNA or RNA) surrounded by a protein coat and/or a membrane
Viroid - answer✔just infect plants, naked RNA (ancient virus?)
Virion - answer✔infectious viral particle
How does viral replication differ from that of bacteria? - answer✔Viruses must assemble using
pre-formed components!
, ©SIRJOEL EXAM SOLUTIONS
10/7/2024 11:03AM
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 - answer✔Virions penetrate the cells. No virus detectable.
Burst/Yield - answer✔Host cells release many viral particles.
Tobacco Mosaic Disease - 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? - 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 - answer✔1. Nature and sequence of nucleic acid in virion
2. Symmetry of protein shell (capsid)
, ©SIRJOEL EXAM SOLUTIONS
10/7/2024 11:03AM
3. Presence or absence of lipid membrane (envelope)
4. Dimensions of virion and capsid
Virus growth curve - answer✔
Virus titer aka Viral load - 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? - 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
10/7/2024 11:03AM
Virology Exam 1 (Columbia - Racaniello)
Questions With Correct Answers
1. How many viruses do we carry at any given time? Why don't these make us sick? - 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? - answer✔Co-evolution, thermotolerant fungi, enteric virus replaces function of
commensal bacteria
What is a virus? - answer✔An infectious, obligate intracellular parasite comprising genetic
material (DNA or RNA) surrounded by a protein coat and/or a membrane
Viroid - answer✔just infect plants, naked RNA (ancient virus?)
Virion - answer✔infectious viral particle
How does viral replication differ from that of bacteria? - answer✔Viruses must assemble using
pre-formed components!
, ©SIRJOEL EXAM SOLUTIONS
10/7/2024 11:03AM
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 - answer✔Virions penetrate the cells. No virus detectable.
Burst/Yield - answer✔Host cells release many viral particles.
Tobacco Mosaic Disease - 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? - 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 - answer✔1. Nature and sequence of nucleic acid in virion
2. Symmetry of protein shell (capsid)
, ©SIRJOEL EXAM SOLUTIONS
10/7/2024 11:03AM
3. Presence or absence of lipid membrane (envelope)
4. Dimensions of virion and capsid
Virus growth curve - answer✔
Virus titer aka Viral load - 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? - 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
