Summer Research Program for Science Teachers

Comparing DNA Sources (and other projects)

Koshi Bharwani
Collegiate School
New York, NY

August 1995


The Summer Research Program for the opportunity to do science and to reflect on the teaching of science;
Dr. Sam Silverstein, founder and Director of the Program;
Jay Dubner, Program Coordinator;
Todd Carter, Anjali Shah and Dr. Ching Wang (members of the Gilliam lab) for their input on science teaching;
Dr. Conrad Gilliam for the opportunity to learn from his lab and participate in the research activities.

Long-term projects for

Advanced Biology/Microbiology/Research in Biology

[Teaching Standard D- Structure time for extended investigations]

1. Question: How would you detect the presence of particles too small to be visualized by the microscope?
This would be an introduction to the Molecular Biology unit or to the Research in Bio course. Students would be required to maintain a record of their thoughts in their journal every day for a week. The idea is for them to face the problems that researchers routinely face and that most protocols are designed to circumvent. [Content Standards Unifying Concepts- Evidence, models, and explanations] [Teaching Standard B- Orchestrate scientific discourse]

2. Question: Are these DNA samples from the same or from different sources?
Students are provided with a few DNA samples (YACs, phage DNA or DNA samples from lab). To answer the question, they will need to use techniques that I will have taught them of micropipetting, restriction site cutting and gel electrophoresis (using labs from DNA Science by Greg Freyer). Time span would be 3 days to teach or demonstrate the techniques and about a week for them to design and implement their experiment and to write up a report with analysis and conclusions.

3. Question: Which gene in the metabolic pathway is mutated in my organism?
Students are provided with bacteria with different mutations in a specific metabolic pathway (will need to be ordered from a lab or a biological supply company). Using techniques of growing colonies on minimal media or minimal media with additional nutrients, students will figure out the answer to the question. Background information on the metabolic pathway in question will have been provided. Time span for this would be two weeks ( since incubation time is required).[Content Standard C- Molecular basis of heredity]

4. Task: To generate a restriction map of a plasmid.
Students are provided with a plasmid and two restriction enzymes. They will have been taught the requisite skills of single- and double-digesting a plasmid. Time span: about a week.

Long term projects for 7th grade Life science

[Teaching Standard D- Structure time for extended investigations]

1. Question: How does the environment affect seed germination/plant growth?
Students test the effect of factors such as water, light, minerals on seed germination or plant growth. They would, in doing so, come up with a design of a controlled experiment and encounter the concept of experimental error. (Time span: about a week or 10 days for taking measurements) [Content Standard Unifying Concepts- Change, constancy, and measurement] [Content Standard A- Understandings about scientific inquiry]

2. Task: To build a model of DNA using different combinations of the 4 bases and to then figure out which combinations are used in actual fact.
Students will thus construct for themselves the rationale behind having A pair with T and G with C. The structure of DNA for them should thus be a little more meaningful. (Time span: 2 days) [Content Standard C- Molecular basis of heredity]

3. Question: Why does lettuce/celery feel different when kept in water compared to when it's not? Does animal tissue (like liver or chicken meat) also feel different?
Students would test one vegetable and one meat under the two conditions (water or no water). They would be permitted the use of a microscope to compare the cell types of the plant and animal material and come up with a hypothesis for the difference. The idea is for them to arrive at the discovery of the effect of having a cell wall and vacuole through thought and experimentation. (Time span: about a week) [Content Standard C- The cell]


Koshi Bharwani

August 1995


Students will come to know that:
a. restriction enzymes are useful tools;
b. gel electrophoresis separates fragments based on size; [Content Standard E- Understandings about science/technology]
c. DNA of the same source will have the same pattern of bands on the gel;
d. RFLP (restriction fragment length polymorphism) analysis, which they frequently hear about in the media, is based on simple scientific principles

Students will know this by:
a. doing restriction site cutting;
b. doing gel electrophoresis
c. reading about this and then designing and implementing their experimental plan to answer the question; [Content Standard A- Design and conduct scientific investigations]
d. doing RFLP analysis

Days 1 and 2: - students have been assigned reading on restriction enzymes from text and the protocols for restriction site cutting and gel electrophoresis; they practice the technique of restriction digest, following the protocol. They run products of restriction cuts on a gel.

Day 3: - students record results and are told that they will be given two projects that require them to use some of these tools and techniques.
- they are told about the two projects:
* Question: Do these DNA samples come from the same or different sources?
* Task: To generate the restriction map of a plasmid.

- Each group of 2/3 students will be given 2 DNA samples and a plasmid to map.
- Criteria for evaluation must be extremely explicit and handed out to students. (Criteria should include lab behavior, evidence of planning and organization, as well as various aspects of the lab report) [Teaching Standard D- Create setting supportive of science inquiry]

Days 4 - 7: Class time for doing experimentation.
Day 9: Due date for lab report
Day 10/11: Teacher evaluation in whole group of experience of this "long-
term" lab project. Some kind of reflection and closure on the part of students. [Teaching Standard B- Orchestrate scientific discourse] [Teaching Standard D- Structure time for extended investigations]

a. Lab reports
b. Evidence of planning, organization and thought while students do the lab.
c. Quiz on content area (principles behind techniques, interpretation of other results) [Teaching Standard C- Use multiple methods to gather data]

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