Beacon Lesson Plan Library

Decoding DNA

Suzan Smith
Marion County Schools


This is the sixth and final lesson plan in the unit, Where We Come From and is an extension activity that reflects the standards for Marion County Schools in Florida for eighth grade. Students complete their KWL charts from the first lesson of the unit as a review for the summative. Then they decode a secret message using the four basic components of DNA, adenine, cytosine, guanine and thymine.


The student knows that the variation in each species is due to the exchange and interaction of genetic information as it is passed from parent to offspring.


-Colored pencils or markers in blue, red, yellow and green
-Student copies of the worksheet, Decoding DNA (associated file)
-10 Prepared Decoder Sheets (associated file)
-Overhead transparency of Decoding DNA (associated file)
-The studentsí KWL Charts that they began on Day 1
-Teacher copy of the file KWL Learned Column (see extensions)
-Presentation system: computer, Internet, large screen TV


1. Review the Weblink and study the following topics: basic substance of DNA, basic components of DNA, scientists related to the study of DNA. (Watson and Crick, Delbruck, and Beadle)
2. Copy and color 10 Decoder Sheets and post them around the room on walls, chalkboard, doors, etc. You may wish to laminate them to use for years to come.
3. Copy the worksheet, Decoding DNA, for each student.
4. Provide coloring supplies in red, green, blue, and red.
5. Arrange access to the studentsí KWL Charts from Day 1.
6. Bookmark the Website and make sure technology equipment is working and ready.


NOTE: The DNA activity is an optional activity, however, the summative test contains a question about DNA. If you choose not to complete procedures 1-5, you may want to remove the DNA question from the test and substitute one of your choice. You can also choose to teach the DNA material in another way besides this activity.

1. Ask the students if they know what DNA is. Briefly discuss some of the basic components of DNA. (such as a double helix, contains all genetic information, and the four amino acid components: adenine, cytosine, guanine, thymine) Put the words on the board, help students to pronounce them and become familiar with them.

2. Visit the Weblink listed below and discuss the toothpick code Beadle and Delbruck created.

3. Tell the students that they will break a secret code today using those four amino acids as their keys.

4. Give out the student copies of Decoding DNA. Go over the directions and instruct the students how to color the worksheet. You will need to model this on an overhead transparency of the Decoding DNA worksheet.

5. When they are finished coloring, the students should take their worksheets to a posted Decoder Sheet (see associated file) and solve the riddle.

6. Once the riddle is solved, students must answer the question at the bottom of their worksheets.

7. Once all students have completed the activity, discuss the riddle and the question with the class. Allow students to correct their answers since this lesson is also a review of the entire unit.

8. Review the genetics vocabulary. (You might have the words on 3 X 5 cards and the definitions/examples on 3 X 5 cards. Give each student a card and instruct them to find the matching card(s). The method of review is up to you.)

9. Instruct students to take out their Probability Questions from the previous lesson. Since you will have formatively assessed these already, allow students to discuss and correct their answers.

10. Take out the overhead/chart of responses students made on the first day of the lesson (see Wild Babies, procedure #9.) Allow time for discussion of the reponses or statements, determining which are correct/incorrect, etc. Review with students the questions that are on the summative test, but don't let them know these are the questions. Allow time for them to comment and encourage them to look at the Individual Questions, Conclusion Questions, and Probability Questions from previous lessons.

11. Return the diagnostic KWL charts. Students are given time to complete the last column of the chart titled, What I Learned. You might want to ask some specific, guided questions to help students. You can choose these from the questions students have been working on during this unit. Since they have the corrected answers with your feedback, students should be able to list the key concepts and ideas they've learned from the unit. You may need to model this if your students have not used KWL charts before.

12. If you have time at the end of class, allow students to share what they listed in the L portion of their charts. Just be sure to have collected them first! Remind students to study since they will take the summative assessment tomorrow.


Formatively assess each student's KWL chart. A key for the L portion is in the associated file.

Formatively assess the Decoding DNA worksheet for completion and a logical answer to the question at the bottom of the worksheet. Since this is covered on the summative assessment, offer feedback and corrective information to those students who don't have the right answer to the question.


The Beacon Unit Plan associated with this lesson can be viewed by clicking on the link located at the top of this page or by using the following URL: Once you select the unitís link, scroll to the bottom of the unit plan page to find the section, Associated Files. This section contains links to the Unit Plan Overview, Diagnostic and Summative Assessments, and other associated files (if any).

Web Links

This Weblink summarizes the basis upon which I created the Decoding DNA activity. On pages 3 and 4 is information about telegrams written between Delbruck and Beadle using the parts of DNA as a coded language. Page 9 contains information about a toothpick model that Delbruck created for Beadle. The answer to his riddle is the same as the answer to my riddle in -Decoding DNA.-
“The Delbruck Molecules”

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