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Experience 1:
The Ladder of Life
Students identify the base pairs guanine, cytosine, thymine and adenine. Students create a DNA model using colored paper clips to resemble these base pairs.
Indiana's Academic Standards
Science
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Standard 7: Common Themes (6.7.2, 7.7.2) |
Language Arts
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Standard 7: Listening and Speaking - Listening and Speaking Skills, Strategies and Applications (6.7.3) |
| You will need... |
Time:
Materials
Per student:
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One class period 40 - 50 minutes |
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Ladder of Life handout |
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6 x 18-inch piece of construction paper (Color does not matter, as long as paper clips are visible.) |
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Jumbo metal paper clips (about 600) |
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Plastic-coated colored paper clips (red, blue, green and yellow) (about 500) |
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four small buckets or containers |
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scotch tape |
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| Teacher Preparation: |
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Separate paper clips by color and size and place into respective buckets or containers |
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Display other DNA models from Websites or posters. |
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Procedures:
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Write the code 4-5-15-24-25-18-9-2-15-14-21-3-12-5-9-3-1-3-9-4 on the board and challenge students to decode the numbers using the alphabet sequence with A=1, B=2, C=3 et cetera. (Code word = deoxyribonucleic acid) |
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Elicit from students what they know about DNA. Explain that the DNA code is like a blueprint for each living thing. The combination of the base pairs determines who, how and what something is. |
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Distribute the Ladder of Life handout. Have students read the top paragraph and discuss what they have read. Challenge students to complete the missing base pairs. Discuss the correct answers when finished. |
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Distribute 20 large paper clips to each student and instruct students to connect 10 large paper clips to resemble one side of a DNA strand. |
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Instruct students to connect the remaining 10 large paper clips to make a second side of the DNA strand. These strands represent the sides of the ladder. Emphasize that DNA is a double-stranded helix. It is like a twisted ladder. |
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Provide students with the key:
A = adenine = red
T = thymine = blue
G = guanine = green
C = cytosine = yellow |
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Display four buckets containing red, blue, green and yellow plastic-coated paper clips. |
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Challenge students to design a DNA strand using eight pairs of the plastic-coated paper clips. Instruct students to place a base pair where each of the large paper clips joins together. |
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Remind students of the following rule: A pairs with T, and G pairs with C. Check to make sure their designs are accurate. |
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After DNA models have been approved, challenge students to locate students in the classroom with an identical DNA strand and discuss their findings. Why would it be difficult to find a match for your DNA in real life? |
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DNA Quick Hits: |
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The sequences formed by the base pairs in our DNA carry our genetic code. |
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We are each unique because of individual variations in the sequence of the base pairs. |
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There are millions of different combinations that can be made using only four base pairs. |
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The DNA models created in class are many, many times larger than a real DNA strand. |
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A human DNA strand is approximately 6 feet long, but it is so small and tightly coiled that it can fit inside the nucleus of a single cell. |
Assessment:
Check each constructed DNA strand making sure red paper clips pair with blue paper clips and green paper clips pair with yellow paper clips. |
