Download Think about what you have learned about the structure of DNA

DNA
Think about what you have learned about the structure of DNA.
Using the section of DNA given, draw in a complete strand of
DNA and label the nitrogen base, phosphate molecule and
sugar molecule. Circle one nucleotide. Explain what would
cause mutation.
DNA
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DNA
Suggested Grade Span
6–8
Task
Think about what you have learned about the structure of DNA. Using the section of DNA given,
draw in a complete strand of DNA 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
DNA structure and replication. The discovery of DNA 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.
DNA
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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 DNA strand, students will
demonstrate their understanding of DNA 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 DNA 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 DNA, 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 DNA 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 DNA, nitrogen base, phosphate molecule and sugar molecule, as well as
the concept of mutation.
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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 DNA "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.
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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 DNA
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 DNA structure and the
correct base pairs, but did not circle or label the appropriate parts. The student demonstrates a
minimal understanding of DNA 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
DNA structure and correct base pairs and labels most of the diagram. The student
demonstrates an understanding of the DNA 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 DNA structure and correct base
pairs and labels the diagram correctly. The student demonstrates an understanding of the DNA
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.
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Novice
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Apprentice
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Practitioner
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Expert
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