DNA DNA. 1 of 9. Copyright 2007, Exemplars, Inc. All rights reserved.

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1 Think about what you have learned about the structure of. Using the section of given, draw in a complete strand of and label the nitrogen base, phosphate molecule and sugar molecule. Circle one nucleotide. Explain what would cause mutation. 1 of 9

2 Suggested Grade Span 6 8 Task Think about what you have learned about the structure of. Using the section of given, draw in a complete strand of and label the nitrogen base, phosphate molecule and sugar molecule. Circle one nucleotide. Explain what would cause mutation. Big Ideas and Unifying Concepts Change and constancy Evolution and equilibrium Form and function Models Systems Life Science Concepts Reproduction and heredity Structure and function Mathematics Concept Diagrams Time Required for the Task One 30-minute class period. Context Our seventh-grade textbook includes a study of cell function: transport mitosis, respiration and structure and replication. The discovery of structure and how it replicates is one of the most important discoveries of our time. Students learned about this discovery and its impact on the world of genetics and cellular biology. 2 of 9

3 What the Task Accomplishes This is a task to use as a more formative assessment to see what the students understand about this fundamental cellular process. By completing a drawing of a strand, students will demonstrate their understanding of components: sugar, phosphate and nitrogen bases. Complementary base pairs and hereditary code (gene sequence) are also addressed. Some students may exhibit awareness of mutagens and the implication resulting from a change in base pair order. How the Student Will Investigate Students will use their prior knowledge and experiences to complete the strand. They will draw in the completed strand and label the components (nitrogen base, phosphate molecule, and sugar molecule). They will then circle one nucleotide and explain what would cause a mutation. Interdisciplinary Links and Extensions Science/Technology This task could be expanded to include a discussion on recombinant, gene manipulation, aging and the Human Genome Project. Teaching Tips and Guiding Questions This task follows a lab activity in which students use beads, paper cutouts or other manipulables to construct a model of the strand and then to make duplicates of the strand. Stages of mitosis should also be reviewed during the lab. Concepts to be Assessed (Unifying concepts and big ideas and science concepts to be assessed using the Exemplars Science Rubric under the criterion: Science Concepts and Related Content) Life Science Structure and Function; Reproduction and Heredity: Students identify characteristics of cells and their functions. (Cells carry on functions needed to sustain life. They grow, divide, take in nutrients, provide energy, and remove wastes. Specialized cells perform specialized functions in multicellular organisms.) Students understand that hereditary information is contained in genes, located in the chromosomes of each cell. Students understand the terms, nitrogen base, phosphate molecule and sugar molecule, as well as the concept of mutation. 3 of 9

4 Scientific Method Models: Students see that how a model works after changes are made to it may suggest how the real thing would work if the same thing were done to it and that choosing a useful model (not too simple/not too complex) to explore concepts encourages insightful and creative thinking in science, mathematics and engineering. Mathematics: Students use diagrams appropriately. Skills to be Developed (Science process skills to be assessed using the Exemplars Science Rubric under the criteria: Scientific Procedures and Reasoning Strategies, and Scientific Communication Using Data) Scientific Method: Predicting, problem solving, creating models, explaining, drawing conclusions, communicating what was learned and challenging misconceptions. Other Science Standards and Concepts Addressed Scientific Method: Students describe, predict, investigate and explain phenomena. Scientific Theory: Students look for evidence that explains why things happen and modify explanations when new observations are made. Life Science Structure and Function: Students can describe important levels of organization for structure and function including cells, organs, tissues, organ systems, organisms and ecosystems. Students can explain that all organisms are composed of cells, that some organisms are single celled, and that others, including humans, are multicellular. Communication: Students use verbal and nonverbal skills to express themselves effectively. Suggested Materials Students will need paper and a pencil. Possible Solutions The completed diagram should show correct complementary base pairs (adenine-thymine, cytosine-guanine), each attached to the deoxyribose sugar molecule. Each sugar is attached to phosphate to form the sides of the "ladder." Any nucleotide consisting of one phosphate, one sugar and one base should be circled. Mutations can occur randomly or by environmental factors (UV rays, carcinogens, etc.) that result in some change of hereditary code. Some answers may show a sketch of changed genetic sequences. 4 of 9

5 Task-Specific Assessment Notes Novice The student's diagram is incomplete and there are no labels. There are circles where there should be another section. The student demonstrates a minimal understanding of structure and appropriate terminology is not used. The student does not explain any mutation. Apprentice The student's diagram is partially complete. The student knows the structure and the correct base pairs, but did not circle or label the appropriate parts. The student demonstrates a minimal understanding of structure and the appropriate terminology is not used. The student does not explain any mutation. Practitioner The student's diagram is complete with only one or two minor errors. The student knows the structure and correct base pairs and labels most of the diagram. The student demonstrates an understanding of the structure. The appropriate terminology is partially used. The student does not explain any mutation. Expert The student's diagram is complete. The student knows the structure and correct base pairs and labels the diagram correctly. The student demonstrates an understanding of the structure and uses appropriate terminology. The student does not explain any mutation. Note: A "true" Expert should illustrate a mutation by drawing a different genetic sequence. 5 of 9

6 Novice 6 of 9

7 Apprentice 7 of 9

8 Practitioner 8 of 9

9 Expert 9 of 9