Nucleic Acids and Protein Synthesis
The challenge in teaching protein synthesis, is how to make an abstract topic tangible and real. Textbook diagrams are just as difficult to follow as reading the text. By using different strategies which involve the students use of all their senses, I attempt to make the genetic code and how it translates into proteins relevant and fun.
First of all, to grab their attention I have students extract DNA from onions, wheat germ, liver, and/or bacteria. They are facinated to see that DNA is a real thing that can be seen and touched and that it is a substance that is in their cells also.
Secondly, to simplify the genetic code, I relate it to the six dot braille code. Students are facinated with the ability of blind persons to read braille and I assure them that it is a very simple code that they can easily learn too. Braille is based on different combinations of six dots. The combinations of six dots in a braille cell make one letter or sign, several letters together make a word, several words make a sentence. There is a capital sign that begins a sentence and a punctuation sign that ends a sentence. In the triplet genetic code of the DNA molecule, the letters are the nitrogen bases, the words are the codons which code for an amino acid, the sentences are the proteins. AUG is the capital sign that starts the protein and there are three codons or punctuation signs to end the protein. If students can understand the braille alphabet, then they will understand the alphabet of the genetic code.
Students get to "play" by cutting out colorful nucleotide models of DNA and RNA and assembling them like a puzzle, replicating the DNA with its complimentary base pairs and transcribing the RNA with its complimentary base pairs. All DNA chains are linked and twisted and hung in the classroom.
Also, I direct the students through an activity of folded paper listing a sequence of bases on one of the folds, having them replicate the sequence into a new DNA strand on another fold, transcribing the sequence onto a messenger RNA strand on yet another fold and finally translating that sequence into transfer RNA anticodons and their corresponding amino acid. Students learn protein synthesis in very short steps and immediately feel that they are mastering a difficult concept.
Finally, students are given various roles in a play of assembling a protein molecule. Each student is given an index card with either a DNA codon, a messenger RNA codon, a transfer RNA anticodon or the name of an amino acid. One student is RNA polymerase and another student is a ribosome. Areas of the classroom become the nucleus and cytoplasm. For the dress rehearsal, as the director, I tell the students where to go, what to do and how to bond to each other. Although they feel awkward at first, they eventually get into it. Then, we make another protein with simpler narration and students seem to know where to go. It's chaotic and fun and students have assured me afterwards that it really helped them to understand how proteins are made.
When we are finished, students have learned the structure of DNA, DNA replication of the genetic code, the structure of RNA and transcription of the genetic code and how DNA codes for and translates into proteins in the ribosomes.
Students are evaluated by their willingness to participate in all the activities, their ability to form conclusions after each activity and by a written test on protein synthesis.
Students are successful in learning the concept of protein synthesis despite its abstract nature because the activities are playful and simple. When they cut out the nucleotide models, they have an opportunity to relax and chat with each other and even listen to a little music in the background. Mixing solutions, smelling the chemicals and watching the DNA strand "magically" spool around the glass rod makes this macromolecule a tangible and real object. Using imagination as students pretend to be molecules acting out protein synthesis and whole body movement is as important a part of learning for high school students as it is for young children.