My Science Box

Lesson Plan

1. Begin class with a secret DNA message for the students to decode (see assessment section of the Secret Codes lesson).
2. Review the steps of the protein synthesis process: 1) DNA is transcribed into messenger RNA and 2) the RNA is translated into a sequence of amino acids based on 3 nucleotide codons.
3. Give students more detailed background information on how the protein synthesis process works. Discuss the role of RNA polymerase and the ribosome. Describe how RNA polymerase recognizes where to start transcribing the gene (a promotor sequence) and how the ribosome knows where to start (AUG) and stop (UAG, UAA, or UGA) translating the messenger RNA.
4. Give students an overview of the rest of the class period. Show students where the nucleus is and where the cytosol is.
5. Assign students their roles. Each student should get an instruction card and the materials listed on their instruction card.
6. Allow students performing the role of the messenger RNA to create RNA nucleotides. Allow students performing the role of the transfer RNA a few minutes to assemble their transfer RNA molecules.
7. Restore silence to the classroom and begin the process. Have all the students watch as the process unfolds. You may want to describe what is going on at each step for the students that aren’t involved directly. Briefly:

   1. RNA polymerase finds the TATAAA promotor sequence on the DNA molecule.
   2. RNA polymerase unzips the DNA nucleotide after the promotor and finds a matching RNA nucleotide.
   3. RNA polymerase unzips the next DNA nucleotide and finds a matching RNA nucleotide.
   4. RNA polymerase joins the RNA nucleotides together.
   5. RNA polymerase continues unzipping, finding nucleotides, and joining them together until the end of the DNA molecule.
   6. DNA zips itself back up again.
   7. The newly assembled messenger RNA floats out of the nucleus to the ribosome.
   8. The ribosome finds the AUG start sequence on the messenger RNA.
   9. The ribosome finds a matching transfer RNA and lines it up alongside the messenger RNA strand.
   10. The ribosome finds a matching transfer RNA to the next 3 nucleotides.
   11. The ribosome removes the amino acid from the first transfer RNA and attaches it to the amino acid that just arrived.
   12. The ribosome continues finding transfer RNA molecules and joining amino acids until it reaches a stop codon (UAG, UAA, or UGA).
   13. The empty transfer RNA molecules leave the ribosome.

8. If there is extra time, you may be able to have students switch roles and go through the process a second time in a new role.
9. You may want to close the class with a discussion of how the classroom protein factory is different than the actual process taking place in nearly every cell in your body. For instance, the DNA molecule in the model only had 1 gene whereas real DNA molecules have thousands of genes. Also, RNA polymerase and ribosomes are just molecules and act like a machine in a factory, not like a thinking human being.