MICR 4423 EXAM PRACTICE QUESTIONS
AND CORRECT ANSWERS!!
What is antibiotic selection?
Survival of a population of antibiotic resistant cells within a larger population of antibiotic
sensitive cells.
Where can antibiotic selection occur?
Anywhere where there are antibiotics and bacteria present. The best-surviving bacteria will be
selected for.
Name a common use for antibiotic selection in microbiological research.
To identify and isolate cells that have piece of DNA of interest such as a particular plasmid or
gene in the chromosome.
Why does virtually every plasmid used for scientific research contain an antibiotic
resistance marker?
It allows the cells that contain that plasmid to be identified through antibiotic selection.
Imagine that you have a sample of bacteria that is a mixture of ampicillin-resistant cells
and ampicillin-sensitive cells. How could you isolate the ampicillin-resistant cells?
Plate the cells on an ampicillin plate so that only the ampicillin-resistant cells will survive and
produce colonies.
What antibiotic or class of antibiotics do cells containing the bla marker become resistant
to? What about aac? What about cat?
Bla- ampicillin/any cillin
Aac- aminoglycosides (usually kanamycin)
Cat- chloramphenicol
What are the Tet-ON and Tet-OFF systems typically used for?
To inducibly or conditionally control gene expression in eukaryotic systems.
, What is a typical inducer of the Tet-ON or Tet-OFF system?
Plain tetracycline or (usually doxycycline)
Distinguish between the Tet-ON and Tet-OFF systems in terms of what inducer addition
does to gene expression and how it occurs at the molecular level.
In Tet-ON when you add tet or dox it turns gene expression on. In Tet-OFF when you add tet or
dox it turns tet expression off. Addition of tetracycline always causes tetR to come off its
operator. In Tet-OFF there is a cruddy promoter that requires a transactivation domain which is
bound to TetR. When TetR leaves it takes the transactivation domain with it and stops gene
expression.
What is a typical way of administering Tet to an animal?
Through its drinking water.
Contrast how antibiotics are regulated in the United States and northern Europe with how
they are regulated in most other countries.
In US- prescribed by a doctor and dispensed by a pharmacist.
Most other countries- over-the-counter in drug stores or even gas stations.
List at least one pro and one con of having antibiotics available by prescription only.
Prescription only pro- professional diagnosis means hopefully the appropriate antibiotic and
course of antibiotics is prescribed, there is more accountability, assurance of product quality...
Con- Requires a lot of infrastructure and money (doctors and pharmacists have to be paid),
slower
List at least one pro and one con of having antibiotics available over the counter.
Pros- faster, cheaper, more available to people in rural areas that do not have access to a doctor
Cons- Risk of inappropriate treatment (people might choose the wrong antibiotic or not take it
for long enough), risk of development of antibiotic resistance.
What is the most prevalent/biggest use of antibiotics worldwide and in the USA?
In agriculture, raising animals for human food consumption.
AND CORRECT ANSWERS!!
What is antibiotic selection?
Survival of a population of antibiotic resistant cells within a larger population of antibiotic
sensitive cells.
Where can antibiotic selection occur?
Anywhere where there are antibiotics and bacteria present. The best-surviving bacteria will be
selected for.
Name a common use for antibiotic selection in microbiological research.
To identify and isolate cells that have piece of DNA of interest such as a particular plasmid or
gene in the chromosome.
Why does virtually every plasmid used for scientific research contain an antibiotic
resistance marker?
It allows the cells that contain that plasmid to be identified through antibiotic selection.
Imagine that you have a sample of bacteria that is a mixture of ampicillin-resistant cells
and ampicillin-sensitive cells. How could you isolate the ampicillin-resistant cells?
Plate the cells on an ampicillin plate so that only the ampicillin-resistant cells will survive and
produce colonies.
What antibiotic or class of antibiotics do cells containing the bla marker become resistant
to? What about aac? What about cat?
Bla- ampicillin/any cillin
Aac- aminoglycosides (usually kanamycin)
Cat- chloramphenicol
What are the Tet-ON and Tet-OFF systems typically used for?
To inducibly or conditionally control gene expression in eukaryotic systems.
, What is a typical inducer of the Tet-ON or Tet-OFF system?
Plain tetracycline or (usually doxycycline)
Distinguish between the Tet-ON and Tet-OFF systems in terms of what inducer addition
does to gene expression and how it occurs at the molecular level.
In Tet-ON when you add tet or dox it turns gene expression on. In Tet-OFF when you add tet or
dox it turns tet expression off. Addition of tetracycline always causes tetR to come off its
operator. In Tet-OFF there is a cruddy promoter that requires a transactivation domain which is
bound to TetR. When TetR leaves it takes the transactivation domain with it and stops gene
expression.
What is a typical way of administering Tet to an animal?
Through its drinking water.
Contrast how antibiotics are regulated in the United States and northern Europe with how
they are regulated in most other countries.
In US- prescribed by a doctor and dispensed by a pharmacist.
Most other countries- over-the-counter in drug stores or even gas stations.
List at least one pro and one con of having antibiotics available by prescription only.
Prescription only pro- professional diagnosis means hopefully the appropriate antibiotic and
course of antibiotics is prescribed, there is more accountability, assurance of product quality...
Con- Requires a lot of infrastructure and money (doctors and pharmacists have to be paid),
slower
List at least one pro and one con of having antibiotics available over the counter.
Pros- faster, cheaper, more available to people in rural areas that do not have access to a doctor
Cons- Risk of inappropriate treatment (people might choose the wrong antibiotic or not take it
for long enough), risk of development of antibiotic resistance.
What is the most prevalent/biggest use of antibiotics worldwide and in the USA?
In agriculture, raising animals for human food consumption.
