PORTAGE LEARNING
14/May/2026 — 9:32 AM
Module 6 Exam - Requires Respondus LockDown Browser + Webcam
Due No due date Points 100 Questions 38 Time Limit 120 Minutes Requires Respondus LockDown Browser
Instructions
Please read the following before beginning the exam:
You must TYPE your work for calculations or give an explanation for short answer questions in order to receive credit.
You may only use the methods and explanations provided by this course for your answers. The use of a method or
explanation that was not taught in this course is a violation of the Academic Integrity Policy.
You MUST only use the exam resource bank that is provided within the exam.
Any equation or constant used on an exam that is not from the exam resource bank and is different from the method
taught in this course will be considered an outside source and a violation of the Academic Integrity Policy.
During module exams you may not use any outside source of information such as the module, problem sets, notes,
Internet, tutor, etc.
The only items you are allowed to have in front of you are your computer, 1-2 pieces of blank scratch paper, a
calculator (non-cell phone), and a pen/pencil.
Your desk should be free of all other items and clutter.
Attempt History
Attempt Time Score
LATEST
Question 1 pts
Resource Bank
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A virologist is studying a newly discovered virus that infects bacteria. In your own words, explain why bacteriophages are
considered excellent models for understanding viral replication, and describe two structural features of complex
bacteriophages (such as T4) that distinguish them from simpler animal viruses.
Answer: Bacteriophages are excellent models because they have relatively simple, well-defined life cycles with clear
lytic and lysogenic phases, and they can be easily cultured in bacterial hosts. Complex bacteriophages like T4 have: (1) A
contractile tail sheath that acts like a molecular syringe, injecting viral DNA through the bacterial cell wall and
membrane; (2) Tail fibers with specific receptor-binding proteins that recognize and attach to unique surface molecules
on host bacteria, determining host specificity. These structures are absent in most animal viruses, which typically enter
via endocytosis or membrane fusion.
Correct!
Question 2 pts
,Resource Bank
Scientific Calculator
The protein coat that surrounds and protects the viral genome is called the __________, and it is composed of smaller subunits
called __________.
Answer: capsid, capsomeres
Correct!
Question 3 pts
Resource Bank
Scientific Calculator
Which of the following statements about viral envelopes is correct?
a) All viruses, including bacteriophages, possess a viral envelope
b) The viral envelope is synthesized de novo by viral enzymes in the cytoplasm
c) The viral envelope is derived from the host cell membrane and contains virus-encoded glycoproteins
d) Enveloped viruses are more resistant to environmental stress than non-enveloped viruses
Correct!
Question 4 pts
Resource Bank
Scientific Calculator
A patient with AIDS develops progressive multifocal leukoencephalopathy (PML). Brain biopsy reveals oligodendrocytes with
enlarged nuclei containing viral particles.
a) Explain why JC virus (a polyomavirus) causes PML primarily in immunocompromised patients, and how the virus accesses
the central nervous system from a latent site. (3 pts)
b) JC virus is a non-enveloped DNA virus. Explain why non-enveloped viruses like JC virus, adenovirus, and poliovirus are
generally more environmentally stable than enveloped viruses such as HIV and influenza, and why this stability affects
transmission routes. (3 pts)
Answer:
a) JC virus establishes latency in the kidneys, bone marrow, and lymphoid tissue of healthy individuals. In
immunocompromised patients (CD4+ counts <200/μL), loss of T-cell surveillance allows viral reactivation. The virus
traffics to the CNS via infected B lymphocytes that cross the blood-brain barrier. In oligodendrocytes, the virus
replicates using host DNA polymerase, causing cell lysis, demyelination, and progressive neurologic deficits.
b) Non-enveloped viruses lack a lipid bilayer envelope, making them resistant to drying, detergents, and organic
solvents. They can survive on surfaces for days to weeks and resist gastric acid, enabling fecal-oral transmission.
Enveloped viruses require intact lipid membranes for infectivity; they are inactivated by drying, soap, alcohol, and low
pH, limiting transmission to direct contact, respiratory droplets, or bodily fluids.
, Correct!
Question 5 pts
Resource Bank
Scientific Calculator
True or False: The viral genome is never replicated before viral attachment and entry into a host cell.
True False
Correct!
Question 6 pts
Resource Bank
Scientific Calculator
In your own words, explain how restriction enzymes in bacteria serve as a defense mechanism against bacteriophage
infection, and why this evolutionary arms race has driven the diversity of both restriction-modification systems and viral
evasion strategies.
Answer: Restriction enzymes (endonucleases) recognize and cleave specific DNA sequences. Bacteria protect their own
DNA by methylating these same sequences, preventing self-destruction. When bacteriophage DNA enters, it is typically
unmethylated and is degraded by restriction enzymes. Phages have evolved multiple evasion strategies: (1) Modifying
their DNA with unusual bases (e.g., 5-hydroxymethylcytosine in T4 phage); (2) Producing proteins that inhibit restriction
enzymes; (3) Rapidly methylating their own DNA upon entry. This evolutionary arms race drives diversity in both
bacterial defense and viral evasion.
Correct!
Question 7 pts
Resource Bank
Scientific Calculator
A virus that infects bacteria is specifically called a __________, and the majority of these viruses have capsids with __________-
sided polygon symmetry.
Answer: bacteriophage, 20 (or icosahedral)
Correct!
Question 8 pts
Resource Bank
Scientific Calculator
14/May/2026 — 9:32 AM
Module 6 Exam - Requires Respondus LockDown Browser + Webcam
Due No due date Points 100 Questions 38 Time Limit 120 Minutes Requires Respondus LockDown Browser
Instructions
Please read the following before beginning the exam:
You must TYPE your work for calculations or give an explanation for short answer questions in order to receive credit.
You may only use the methods and explanations provided by this course for your answers. The use of a method or
explanation that was not taught in this course is a violation of the Academic Integrity Policy.
You MUST only use the exam resource bank that is provided within the exam.
Any equation or constant used on an exam that is not from the exam resource bank and is different from the method
taught in this course will be considered an outside source and a violation of the Academic Integrity Policy.
During module exams you may not use any outside source of information such as the module, problem sets, notes,
Internet, tutor, etc.
The only items you are allowed to have in front of you are your computer, 1-2 pieces of blank scratch paper, a
calculator (non-cell phone), and a pen/pencil.
Your desk should be free of all other items and clutter.
Attempt History
Attempt Time Score
LATEST
Question 1 pts
Resource Bank
Scientific Calculator
A virologist is studying a newly discovered virus that infects bacteria. In your own words, explain why bacteriophages are
considered excellent models for understanding viral replication, and describe two structural features of complex
bacteriophages (such as T4) that distinguish them from simpler animal viruses.
Answer: Bacteriophages are excellent models because they have relatively simple, well-defined life cycles with clear
lytic and lysogenic phases, and they can be easily cultured in bacterial hosts. Complex bacteriophages like T4 have: (1) A
contractile tail sheath that acts like a molecular syringe, injecting viral DNA through the bacterial cell wall and
membrane; (2) Tail fibers with specific receptor-binding proteins that recognize and attach to unique surface molecules
on host bacteria, determining host specificity. These structures are absent in most animal viruses, which typically enter
via endocytosis or membrane fusion.
Correct!
Question 2 pts
,Resource Bank
Scientific Calculator
The protein coat that surrounds and protects the viral genome is called the __________, and it is composed of smaller subunits
called __________.
Answer: capsid, capsomeres
Correct!
Question 3 pts
Resource Bank
Scientific Calculator
Which of the following statements about viral envelopes is correct?
a) All viruses, including bacteriophages, possess a viral envelope
b) The viral envelope is synthesized de novo by viral enzymes in the cytoplasm
c) The viral envelope is derived from the host cell membrane and contains virus-encoded glycoproteins
d) Enveloped viruses are more resistant to environmental stress than non-enveloped viruses
Correct!
Question 4 pts
Resource Bank
Scientific Calculator
A patient with AIDS develops progressive multifocal leukoencephalopathy (PML). Brain biopsy reveals oligodendrocytes with
enlarged nuclei containing viral particles.
a) Explain why JC virus (a polyomavirus) causes PML primarily in immunocompromised patients, and how the virus accesses
the central nervous system from a latent site. (3 pts)
b) JC virus is a non-enveloped DNA virus. Explain why non-enveloped viruses like JC virus, adenovirus, and poliovirus are
generally more environmentally stable than enveloped viruses such as HIV and influenza, and why this stability affects
transmission routes. (3 pts)
Answer:
a) JC virus establishes latency in the kidneys, bone marrow, and lymphoid tissue of healthy individuals. In
immunocompromised patients (CD4+ counts <200/μL), loss of T-cell surveillance allows viral reactivation. The virus
traffics to the CNS via infected B lymphocytes that cross the blood-brain barrier. In oligodendrocytes, the virus
replicates using host DNA polymerase, causing cell lysis, demyelination, and progressive neurologic deficits.
b) Non-enveloped viruses lack a lipid bilayer envelope, making them resistant to drying, detergents, and organic
solvents. They can survive on surfaces for days to weeks and resist gastric acid, enabling fecal-oral transmission.
Enveloped viruses require intact lipid membranes for infectivity; they are inactivated by drying, soap, alcohol, and low
pH, limiting transmission to direct contact, respiratory droplets, or bodily fluids.
, Correct!
Question 5 pts
Resource Bank
Scientific Calculator
True or False: The viral genome is never replicated before viral attachment and entry into a host cell.
True False
Correct!
Question 6 pts
Resource Bank
Scientific Calculator
In your own words, explain how restriction enzymes in bacteria serve as a defense mechanism against bacteriophage
infection, and why this evolutionary arms race has driven the diversity of both restriction-modification systems and viral
evasion strategies.
Answer: Restriction enzymes (endonucleases) recognize and cleave specific DNA sequences. Bacteria protect their own
DNA by methylating these same sequences, preventing self-destruction. When bacteriophage DNA enters, it is typically
unmethylated and is degraded by restriction enzymes. Phages have evolved multiple evasion strategies: (1) Modifying
their DNA with unusual bases (e.g., 5-hydroxymethylcytosine in T4 phage); (2) Producing proteins that inhibit restriction
enzymes; (3) Rapidly methylating their own DNA upon entry. This evolutionary arms race drives diversity in both
bacterial defense and viral evasion.
Correct!
Question 7 pts
Resource Bank
Scientific Calculator
A virus that infects bacteria is specifically called a __________, and the majority of these viruses have capsids with __________-
sided polygon symmetry.
Answer: bacteriophage, 20 (or icosahedral)
Correct!
Question 8 pts
Resource Bank
Scientific Calculator
