MICR 4423 Exam 5 Questions and
Answers
What is antibiotic selection? - Answer-Survival of a population of antibiotic resistant cells within a larger
population of antibiotic sensitive cells.
Where can antibiotic selection occur? - Answer-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. - Answer-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? -
Answer-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? - Answer-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? - Answer-Bla- ampicillin/any cillin
, Aac- aminoglycosides (usually kanamycin)
Cat- chloramphenicol
What are the Tet-ON and Tet-OFF systems typically used for? - Answer-To inducibly or conditionally
control gene expression in eukaryotic systems.
What is a typical inducer of the Tet-ON or Tet-OFF system? - Answer-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. - Answer-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? - Answer-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. - Answer-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. - Answer-
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. - Answer-Pros- faster,
cheaper, more available to people in rural areas that do not have access to a doctor
Answers
What is antibiotic selection? - Answer-Survival of a population of antibiotic resistant cells within a larger
population of antibiotic sensitive cells.
Where can antibiotic selection occur? - Answer-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. - Answer-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? -
Answer-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? - Answer-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? - Answer-Bla- ampicillin/any cillin
, Aac- aminoglycosides (usually kanamycin)
Cat- chloramphenicol
What are the Tet-ON and Tet-OFF systems typically used for? - Answer-To inducibly or conditionally
control gene expression in eukaryotic systems.
What is a typical inducer of the Tet-ON or Tet-OFF system? - Answer-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. - Answer-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? - Answer-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. - Answer-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. - Answer-
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. - Answer-Pros- faster,
cheaper, more available to people in rural areas that do not have access to a doctor
