MICR 221 - FINAL EXAM 2026
(BANFIELD) COMPLETE QUESTIONS
AND ANSWERS
\.T/F: viruses always kill the host - ANSWERS✔-false; require a place to live
\.T/F: hosts fully kill all traces of virus - ANSWERS✔-false; by fully killing the virus,
it enables new pathogens to enter
\.Example of Beneficial Host-Virus Relationships (2) - ANSWERS✔-
1. Host - worm
Virus - polydnavirus from wasp eggs (prevents destruction of eggs in worm)
2. HERVs (retrovirus) causes residual glycoprotein in trophoblasts which fuse to
form syntitotrophoblast (leads to placental formation)
\.HERVs - ANSWERS✔-human endogenous retroviruses that drive the evolution of
the placenta
\.Which of the following statements are TRUE?
A. Least amount of biological diversity in viruses relative to other biological
kingdoms
B. It is important to study virus/host interactions in order to defend against viruses
C. Viruses are extracellular parasites
,D. Hosts fully kill all traces of viruses
E. Viruses kill of the host during infection - ANSWERS✔-B
\.CRISPER-Cas9 Genome Editing - ANSWERS✔--bacterium detects presence of
virus DNA
-produces two short RNA (one contains sequence matching that of invading virus)
-two RNA form complex with CAS 9 nuclease
-complex invades nucleus and locks to PAN sequence
-guide RNA (one with matching sequence to target) finds viral DNA
-CAS 9 uses molecular scissors to cut out viral DNA enabling cell to repair cut
(error prone) leading to mutations to disable gene
-crisper system cut = DNA template can pair up with cut ends and replace with
new error-free version
\.T/F: the CRISPER Cas-9 genome editing system degrades only the viral DNA gene
- ANSWERS✔-true via molecular scissors and replaces with new error free one
(guide RNA enables detection of viral DNA gene sequence)
\.Why are we not always sick by viruses infection? (3) - ANSWERS✔-1. Host
Defences (immune system)
2. Microbial Specificity (very few viruses that can interact with specific human
receptors)
3. Inapparent Functions (no symptoms)
,\.T/F: Viruses are the most abundant biological entity in the oceans and second
largest component of biomass after prokaryotes - ANSWERS✔-true
\.Characteristics of a Virus - ANSWERS✔-- very small size (typically not viewed via
light microscope)
- produced from assembly of pre-formed components
- virus particles do not grow
- do not encode info for energy production, ribosomes, tRNAs, or lipid membrane
synthesis
\.Which of the following is a characteristic of a virus?
A. growth
B. encoding info for energy production
C. contains rRNA and tRNA
D. large size
E. cannot synthesize lipid membranes - ANSWERS✔-E
\._______ is a massive virus, assembled from pre-formed components that infects
algae - ANSWERS✔-Mimivirus
\.5-Part Strategy for Virus Definition - ANSWERS✔-1. Build small particles
containing nucleic acid genome
2. Small genomes
3. Infectious cycle
, 4. Relationship with host (benign or lethal)
5. Overcome host defenses
\.T/F: viruses cannot contain viruses within them - ANSWERS✔-false; i.e.
Mimivirus containing microvirus, Sputnik
\.Plaque Assay - ANSWERS✔-Way of determine how much virus you have;
quantitation of virus
\.________ is a technique used to quantify infectious virus production. -
ANSWERS✔-Plaque Assay
\.General Method of Plaque Assay - ANSWERS✔--performing 10 fold dilutions of
virus
-dead cells form plaque
-becoming visible
-counting plaques formed will determine infectious viruses
\.T/F: Plaque Assay can tell you the number of virus particles but NOT the number
of infectious viruses - ANSWERS✔-false; determines plaques formed (viruses that
died from infecting cells) therefore determines number of infectious viruses BUT
NOT number of virus particles
\.Fertilized chicken eggs as a host for viruses - ANSWERS✔--chorioallantoic
membrane acts as reservoir for virus
(BANFIELD) COMPLETE QUESTIONS
AND ANSWERS
\.T/F: viruses always kill the host - ANSWERS✔-false; require a place to live
\.T/F: hosts fully kill all traces of virus - ANSWERS✔-false; by fully killing the virus,
it enables new pathogens to enter
\.Example of Beneficial Host-Virus Relationships (2) - ANSWERS✔-
1. Host - worm
Virus - polydnavirus from wasp eggs (prevents destruction of eggs in worm)
2. HERVs (retrovirus) causes residual glycoprotein in trophoblasts which fuse to
form syntitotrophoblast (leads to placental formation)
\.HERVs - ANSWERS✔-human endogenous retroviruses that drive the evolution of
the placenta
\.Which of the following statements are TRUE?
A. Least amount of biological diversity in viruses relative to other biological
kingdoms
B. It is important to study virus/host interactions in order to defend against viruses
C. Viruses are extracellular parasites
,D. Hosts fully kill all traces of viruses
E. Viruses kill of the host during infection - ANSWERS✔-B
\.CRISPER-Cas9 Genome Editing - ANSWERS✔--bacterium detects presence of
virus DNA
-produces two short RNA (one contains sequence matching that of invading virus)
-two RNA form complex with CAS 9 nuclease
-complex invades nucleus and locks to PAN sequence
-guide RNA (one with matching sequence to target) finds viral DNA
-CAS 9 uses molecular scissors to cut out viral DNA enabling cell to repair cut
(error prone) leading to mutations to disable gene
-crisper system cut = DNA template can pair up with cut ends and replace with
new error-free version
\.T/F: the CRISPER Cas-9 genome editing system degrades only the viral DNA gene
- ANSWERS✔-true via molecular scissors and replaces with new error free one
(guide RNA enables detection of viral DNA gene sequence)
\.Why are we not always sick by viruses infection? (3) - ANSWERS✔-1. Host
Defences (immune system)
2. Microbial Specificity (very few viruses that can interact with specific human
receptors)
3. Inapparent Functions (no symptoms)
,\.T/F: Viruses are the most abundant biological entity in the oceans and second
largest component of biomass after prokaryotes - ANSWERS✔-true
\.Characteristics of a Virus - ANSWERS✔-- very small size (typically not viewed via
light microscope)
- produced from assembly of pre-formed components
- virus particles do not grow
- do not encode info for energy production, ribosomes, tRNAs, or lipid membrane
synthesis
\.Which of the following is a characteristic of a virus?
A. growth
B. encoding info for energy production
C. contains rRNA and tRNA
D. large size
E. cannot synthesize lipid membranes - ANSWERS✔-E
\._______ is a massive virus, assembled from pre-formed components that infects
algae - ANSWERS✔-Mimivirus
\.5-Part Strategy for Virus Definition - ANSWERS✔-1. Build small particles
containing nucleic acid genome
2. Small genomes
3. Infectious cycle
, 4. Relationship with host (benign or lethal)
5. Overcome host defenses
\.T/F: viruses cannot contain viruses within them - ANSWERS✔-false; i.e.
Mimivirus containing microvirus, Sputnik
\.Plaque Assay - ANSWERS✔-Way of determine how much virus you have;
quantitation of virus
\.________ is a technique used to quantify infectious virus production. -
ANSWERS✔-Plaque Assay
\.General Method of Plaque Assay - ANSWERS✔--performing 10 fold dilutions of
virus
-dead cells form plaque
-becoming visible
-counting plaques formed will determine infectious viruses
\.T/F: Plaque Assay can tell you the number of virus particles but NOT the number
of infectious viruses - ANSWERS✔-false; determines plaques formed (viruses that
died from infecting cells) therefore determines number of infectious viruses BUT
NOT number of virus particles
\.Fertilized chicken eggs as a host for viruses - ANSWERS✔--chorioallantoic
membrane acts as reservoir for virus
