Investigating DNA is a set of activities selected for students in a high school biology course, as well as a model for organizing and managing instruction in a high school science class. An observation of a class where students are working on Investigating DNA would show students arriving to the classroom, organizing themselves into their working groups, referring to their calendars and to written instructions, and assembling needed materials with very little direction from the teacher.
A variety of student activities would follow, including: preparing human chromosome spreads, separating a mixture of dyes using gel electrophoresis, extracting DNA from onion cells, using video and CD resources to study the history of the discovery of the DNA structure, and preparing to teach a parent or other adult about DNA structure.
The teacher would be involved as a facilitator and coach: answering student questions, modeling techniques, asking questions to check for understanding, and helping the students evaluate their work. Students learn basic techniques of modern biology, the story of the discovery of DNA, and the structure and properties of DNA. They also learn to work as a team, manage their time in the classroom and lab, follow written and demonstrated procedures, and evaluate their own work. Investigating DNA includes a rationale for this approach, strategies for managing the activities, a description of each activity and a listing of resources available.
INFORMATION FOR THE TEACHER
high school biology
TYPES OF ACTIVITIES
Laboratory, multimedia and cooperative learning
Approximately 12 hours to complete all the activities. Times given for individual activities include preparation and clean-up. Activities have been done on both a 45 minute period and a 90 minute period schedule.
working in teams and advance planning for team work, measuring volume using pipettes and graduated cylinders, micropipetting, and gel electrophoresis
STRATEGY AND RATIONALE
Students self-select cooperative learning teams and plan their own schedule for completing the activities. The teams are given a description of the required assignments which includes approximate times required for completing labs. Each team is also given a blank calendar, a deadline for completion of all the work and a schedule for any whole-class activities. Teams schedule their work on the calendars, which are then are then reviewed by the teacher in order to set up a schedule for the class to ensure that lab space, materials and computers will be available as needed by each team. Teams may need to make changes on their calendars if conflicts occur.
Two stations were set up for each of the three labs. Equipment and materials as well as detailed, written procedures were provided at each station. There was also a Lab Data Record Book for each station in which teams working at that station recorded their data and results. Teacher preparation is demanding; three different labs must be set up and written procedures for each must be very clear. However, there are significant advantages: less equipment is needed (all students can make and run an electrophoresis gel using only two sets of apparatus); the lab set ups are used for a couple of weeks and no additional lab prep work is required during that time. More important, I have found it much easier to monitor for good lab technique and spend time with individual groups as they do the lab work when only one or two groups are working on a specific lab at one time. I have also found that students who complete a lab are eager to answer questions and help those who come after. This relieves me of some of the simpler questions and allows more time for questioning groups about their understanding of the labs.
The activities, as written, also require a multimedia station (at least a computer with a CD drive), a TV/VCR and some computers for word processing.
Each activity is reviewed with the teacher as it is completed by the students. Students get immediate feedback about the accuracy and completeness of their work and they have the opportunity to make corrections and modifications as needed to improve the quality of their work. I have found that students respond very positively to this approach and that the quality of their work improves. A definite learning agenda is communicated to students, they are involved in the planning process and then held accountable for meeting the established objectives. For grading purposes, each scheduled activity is assigned a point value and evaluated immediately upon completion by at least one teacher and one group member. All students are active participants in the instructional activities, and are able to refer to written directions and request assistance from the teacher which helps them complete assignments without frustration.
INFORMATION FOR THE STUDENT
- View the movie The Race for the Double Helix (about 100 minutes). This is a whole class activity, and is scheduled for (specify date). Be sure to record this on your team calendar and keep this day free. As you view the film your team should make a record of
- In the lab, prepare, permanently mount, observe and draw a chromosome spread (about 60 minutes). Use the materials and follow the procedure available at either Lab Station 1 or 2. Be sure to make a data record including procedure, observations and drawings in the Lab Station Data Record Book. Submit your completed slide, and go over your data record with the teacher. With the teacher, take a photograph through the microscope (a micrograph) of your slide. These will be developed and displayed at the end of the unit.
- Before you start this lab, go to the TV/VCR and view the segment of tape showing the procedure for gel electrophoresis. In the lab, you will separate a mixture of dyes using gel electrophoresis (about 90 minutes). Use the materials and equipment available at either Lab Station 3 or 4. Follow the procedure carefully; recording your data in the Lab Station Data Record Book. Schedule two class periods for completing this activity. Show your gel as well as your colored drawing of the gel in your Data Record Book to the teacher when you are finished.
- In the lab, extract DNA from onion cells (about 60 minutes). First go to the TV/VCR and view the segment of video labeled DNA spooling. Use the materials and protocol provided at either Lab Station 5 or 6. Record data in the Lab Station Data Record Book. After you have rinsed your DNA off the glass spooling rod and resuspended it in TE buffer, label the tube and give it to the teacher to put in the refrigerator; your data record will be checked then.
- At the multimedia center, use the materials available on the Life Story CD as well as your notes from the film, Race for the Double Helix, to write a new article about the discovery of the structure of DNA. Your article should be similar in form to the articles from Science News that you have summarized throughout the year. Look at some of the recent Science News magazines available in the class library. Type your article, and print it out. These will be presented orally in class on (specify date).
- Read the materials available in the class library file about The Case of Nathaniel Wu. Complete the assignment according to the directions that follow the reading.
- Learn about the structure of DNA from one or more of the biology textbooks in the class library. Make up a short test which you would give to someone to find out whether they had learned that information. Type the test on the computer and print out a copy for each member of your team.
- Make a model of DNA. Use may use the pipe cleaners, clay and colored paper available in the classroom -- or any other materials which you can get and want to use.
- This activity must be done individually by each team member. Teach one of your parents, or any other adult in your household, about the structure of DNA. Give them the test you made up to test their learning, and your teaching. Grade the test. Reteach and retest if necessary to be sure that they know the material. When you are finished, ask the parent to sign the test. Bring it back to class.
This unit was initially conceived by Christina Zschoche, based on an instructional model that I use for my ChemCom classes, and developed collaboratively for a biology class which the two of us team taught three years ago. It has since been extended and modified by both of us for use in our own classes.
- The Race for the Double Helix was taped from the Arts and Entertainment network. This was a rebroadcast of the BBC Life Story movie.
- The chromosome spread materials are available as a kit, Preparation of Human Chromosome Spreads, from Cell Serv ,Room 103 McCort-Ward Building, The Catholic University of America, Washington D.C. 20064 Phone: (202) 319-2725 Fax: (202) 391-4467.
- Micklos/Cold Spring Harbor video available from Carolina Biological. Several separation of dye mix kits are available from commercial suppliers including Edvotek, Carolina Biological and Wards. If you have gel electrophoresis materials and would like to avoid buying a kit, I would be happy to email the procedure I use. AELPierce@AOL.com
- The videotape of DNA spooling was made by our students, and shows some successful and less than successful DNA spooling efforts. The onion extraction procedure is Judy Brown's, from the NABT Biotechnology Sourcebook. We have previously used successfully the DNA extraction from liver procedure described in The Biology Teacher, February 1993.
- The Life Story CD is available from Wings for Learning. It includes video clips from the movie as well as many supporting materials including, interviews, biographies and science information related to the discovery of the DNA double helix structure.
- The Case of Nathaniel Wu is part of the BSCS module, The Human Genome.