TITLE: Modeling the Structure of DNA
TASK DEVELOPER: K. Sayad
CONTENT AREA AND GRADE: Biology 9-12
SCOPE AND SEQUENCE: Chapter 9 section 2
TARGET TEACHING DATE: April 24-25, 2007
SCHOOL: John F. Kennedy High School

SCIENTIFIC PROCESSES - GRADES 9-12

STANDARD 5.1 SCIENTIFIC PROCESSES: All students will develop problem-solving, decision-making and inquiry skills, reflected by formulating usable questions and hypotheses, planning experiments, conducting systematic observations, interpreting and analyzing data, drawing conclusions, and communicating results.

Strand A. Habits of Mind: Building upon knowledge and skills gained in preceding grades, by the end of Grade 12, students will:

3. Engage in collaboration, peer review, and accurate reporting of findings.

Strand B. Inquiry and Problem Solving: Building upon knowledge and skills gained in preceding grades, by the end of Grade 12, students will:

2. Show that experimental results can lead to new questions and further investigations.

STANDARD 5.5 CHARACTERISTICS OF LIFE: All students will gain an understanding of the structure, characteristics, and basic needs of organisms and will investigate the diversity of life.

Strand C. Reproduction and Heredity: Building upon knowledge and skills gained in preceding grades, by the end of Grade 12, students will:

1. Describe how information is encoded and transmitted in genetic material.
3. Assess the impact of current and emerging technologies on our understanding of inherited human characteristics.

STANDARD 5.2 SCIENCE AND SOCIETY: All students will develop an understanding of how people of various cultures have contributed to the advancement of science and technology, and how major discoveries and events have advanced science and technology.

Strand B. Historical Perspectives: Building upon knowledge and skills gained in preceding grades, by the end of Grade 12, students will:

1. Examine the lives and contributions of important scientists who effected major breakthroughs in our understanding of the natural and designed world.
2. Discuss significant technological achievements in which science has played an important part as well as technological advances that have contributed directly to the advancement of scientific knowledge.
3. Describe the historical origin of important scientific developments such as atomic theory, genetics, plate tectonics, etc., showing how scientific theories develop, are tested, and can be replaced or modified in light of new information and improved investigative techniques.

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The students will construct a model, several base pairs long, of Deoxyribonucleic Acid using plastic drinking straws, styrofoam balls and pipe cleaners. These models will be displayed in the classroom for peer review and will be graded on accuracy and completion of task. The models can be linked together to create a longer chain which can be used in the classroom as a  fun decoration.

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Real World Setting: Historical laboratory research

You are Watson and Crick. You are faced with creating a three dimensional model of the DNA molecule. You must show how the complementary base pairing occurs and how the structure creates the molecules characteristic double helix structure. Once you have completed your model containing several (5-6) nucleotide base pairs, you will present your model to the class and it will be attached to the classroom strand of DNA on display.

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Student Involvement - The students will complete the task as a cooperative group of 2.

Instruction - Activities will be organized and delivered as a teacher-facilitated set of hands-on activities.

Special Education Accommodations - Students with special needs will require the following student responses:

Alternative ways of completing assignments, these students may need to be paired with a student who has better hand eye coordination, these students may require some extra time and possibly a "head start" with this activity. Some suggestions are to partially complete the model and have the student finish it.

Special Education Accommodations - Students with special needs will require the following presentation of information:

Written or photocopied notes of orally presented instruction or assessment materials.
Advance notice of assignment.

Use of Resources - The school will provide: The styrofoam balls to represent the phosphate and sugar backbone and the plastic drinking straws to represent the nucleic acid base pairs. Also provided will be the pipe cleaners to represent the hydrogen bonding and add stability to the model. Classroom time will also be provided.

Use of Resources - The students will provide classroom materials such as pencils, paper, notebooks.

Customer for Student Work - The student will present their work as evidence of task completion to peers, teachers. and students in other grade levels.

Assessment of Student Work - The following people will be involved in assessing student work generated to complete the task: The student's teacher, the student's self evaluation, peers.

Assessment of Student Work - The following forms of assessment will be used to determine progress and results: Exhibition.

Reporting Results - The assessment results will be reported as a letter grade.

Timeline - The estimated time needed to plan, teach, and score this task is one to three class periods.

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Scaffolding for Success

Day One - Activity: Material handout
Estimated Time: 4.0min.

Step 1: Each group of students will receive a bag containing the material for building a model of DNA 5-6 nucleotide bases long.

Step 2: Students are instructed to separate their materials and check to make sure they have all necessary items. At this time some students may need some help organizing this and some may need extra supplies.

Step 3: Students are given the instructions and begin to work on their models.

Technology: NA
Materials: 24 styrofoam balls (12 small and 12 large) for each group. Straws precut one group cut in a "V" and the other group cut using a "U" to represent the nucleotide bases. Red, Green, Blue and White.They will fit together like puzzle pieces. Pipe cleaners, any color.
Scoring Tool: NA

Day One - Activity Two: Assembly of DNA model
Estimated Time: 50 min.

Step 1: Each student follows the directions to assemble the DNA molecule . Small styrofoam balls are used for phosphate, larger balls are connected with pipe cleaners  to represent deoxyribose and the straws are connected to represent the nitrogen bases.

Step 2: Once several nucleotides are assembled the instructor checks the assembly and grades the student based on completion and correctness.

Step 3: Nucleotides are joined together using pipe cleaners and twisted into the helical shape, this can be hung in the classroom and used as a visual aid of again for replication in the future.

Technology: NA
Materials: above
Student Product or Performance: task completion
Scoring Tool: rubric

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Results

The best method to use with this lesson is to show the class a sample of the finished model and allow the students to progress at their own pace. As you circulate through the class they proceed with the model and begin to finish up. It is always best to keep an extra set of materials for those groups that lose or misplace their materials.

Out of a group of 30 students, 25 received a score of B or better with 10 As. Four received a score of C and only one student who refused to do anything received a score of D. This student has difficulty with other students in the class and often chooses to avoid any type of hands on activity. He is perfectly capable of performing along with the rest of the class as demonstrated when he is on a one-to-one basis. He learns more efficiently from listening and reading than from hands on.

This activity could be improved by using edible sources but then you need to count on student consumption and storage or display options. I don't like to leave food or candy around the class room.

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