Protein Synthesis Activities
Tamsen K. Meyer and Cheryl H. Powers
1994 Woodrow Wilson Biology Institute
A Protein Synthesis Analogy
Marvin Minsky in The Society of Minds asks and answers: "How do we ever understand anything? I think, by using one or another kind of analogy - that is, representing each new thing as though it resembles something we already know." Glynn (1988) defines an analogy as a mapping between similar features of concepts, principles, or formulas that are otherwise dissimilar. Analogies allow students to think about complex and abstract subjects in simple or familiar terms. Abstract concepts are qualitatively different from their concrete counterparts; the abstract concept is often ambiguous, defined by symbolism rather than direct perception and the understanding of the abstract concept usually depends on the mastery of a substrate of underlying concepts. Use of an analogy provides a bridge to access the abstract concept. The learner first recalls the analogy; this then stimulates recall of what is known about the new concept by reconstructing the nature of the "is like" relationship represented in the analogy (Newby and Stepich, 1987).
Biology abounds with anthropomorphic terms to describe everything from "messenger RNA" to "daughter cells" with associated visual imagery. The DNA code is in an alphabet spelled with four letters, the structure of DNA is described as a spiral staircase, and some genes are described as "selfish." The cell membrane is the gatekeeper, the Golgi apparatus the packaging department, the mitochondrion a power plant, and the lysosome is the suicide sac or stomach of the cell. Neurobiologists compare the working of the brain to a computer and computer scientists are trying to design computers that work like the human brain - an interesting application of the dual nature and function of analogies!
There are many analogies that teachers have developed to represent the process of protein synthesis. Teachers may adapt this pedagogical strategy to any analogy that works for the abstract idea that is introduced.
- For the candy factory/protein synthesis analogy, first show students a transparency of the fanciful process of manufacturing candy at "Frieda's Candy Factory." Talk about Frieda, the boss who sits in her office all day handing out recipe cards to messengers who go out to the various assembly stations on the factory floor and direct the assembly of ingredients that correspond to the recipes. Combinations of ingredients must pass through several work stations before they end up as candy - the desired product of the factory.
- Ask students to think about proteins and how they are produced in the cell. Next put the transparency of protein synthesis as an overlay over the candy factory and ask students to discuss the process of protein synthesis. The office becomes the nucleus, the work stations the ribosomes, the messenger the mRNA, the workers the tRNA and the ingredients are the amino acids. Removing the candy factory transparency and adding another overlay that simplifies the process into six key steps completes this instructional strategy. Conclude by discussing the degree to which the analogy "fits" the process and the key differences between the model and the target concept.
Dreistadt, Roy. 1968. An analysis of the use of analogies and metaphors in science. Journal of Psychology 68: 97-116.
Glynn, Shawn. 1988. The teaching-with-analogies model: explaining concepts in expository texts. K.D. Muth ed. Children's Comprehension of Narrative and Expository Text. Newark, DE: International Reading Assn.
Minsky, Marvin. 1985. The Society of Minds. New York: Simon and Schuster.
Newby, Timothy and Stepich, Donald. 1987. Learning abstract concepts: the use of analogies as mediational strategy. Journal of Instructional Development 10(2):20-26.
These six steps and their comparison processes in the candy factory are listed below:
Simulation: Protein Synthesis
Protein synthesis is one of the more abstract concepts for biology students to comprehend. Since even the most worldly teenagers like to role play, a simulation of this process helps students visualize the events in the sequence. This teacher-guided activity can be done in one class period if materials are prepared ahead of time. The teacher may modify this lab to fit the level and size of a particular class. It is accompanied by two brief additional activities. All three are designed to introduce and reinforce understanding of protein synthesis.
- index cards - write the anticodon on one side of the index card, the appropriate amino acid on the other side of the card - for example : GCU/ Alanine
- transparent tape - to attach index cards to board
- markers - select two different colors
- paper strips - cut two strips, one approximately 8"x 72", the other 6" x 72" (grocery bags make a strong banner)
- - label the wider strip with a double stranded sequence of DNA, the narrower strip with a complementary sequence of single-stranded mRNA
(the teacher will need to describe and orchestrate the activity for the class)
- One student is a DNA molecule and wears a double stranded sequence of A's, T's, C's and G's.
- A second student wears a single stranded sequence of complementary mRNA.
- This mRNA model takes his/her strand to the board upon which is drawn a ribosome. Another student is the rRNA and will direct the synthesis of the protein. He/she tapes the strand of mRNA to the board on the ribosome. This strand can be "moved along" as transcription and translation occur. The mRNA strand should be long enough so every student participates in building a protein (or at least the polypeptide).
- Each student is given an index card with a tRNA base which codes for a specific amino acid. Students individually match their anticodon to the correct mRNA codon until a chain of amino acids is constructed. Stop and Start codons are included in the set of cards to initiate and terminate the process.
- Upon completion of the simulation and after discussion, students are assigned to lab groups, first to translate into English a coded "message," and next to send a message of their choice (well almost!) to another student in another lab group. Students use a code sheet where the RNA codes for the 20 amino acids have been assigned letters of the alphabet (the six least-used letters have been omitted). Each student must encode and decode in the activity.
- The final exercise in this series is designed to demonstrate student understanding by reviewing the steps in the synthesis process. The students complete the activity by writing an explanation demonstrating their understanding.
This simulation is an adaptation of an activity by Joseph D. Ruhl found in the NABT publication Labs From Outstanding Biology Teachers.
What a Difference an 'A' Makes!!
This activity is designed to follow the Protein Synthesis Simulation where students have walked through the coding of a protein in order to understand how codons and anticodons work inside a living cell - a concrete example of a complex concept!! The exercise is considerably more abstract and will ultimately let you know who understands the mechanisms of this process.
I. DNA and RNA
The model on the left side of the chart represents a segment of a single strand of DNA that has separated from its partner. Using the pictured strand as the original template, construct the following:
- the sequence of bases in the new strand of DNA if the original strand were to replicate
- the sequence of bases in the mRNA produced from the original DNA
- the sequence of bases needed by the tRNA's if they were to pair with the mRNA in #2 above
- the sequence of amino acids that would be assembled in the polypeptide chain. (NOTE: use a chart of mRNA codons such as those found in Miller/Levine Biology).
(A) Assume that the base in position 6 of the original DNA strand mutates to an "A." How will the sequence of 1,2,3, and 4 be affected?
(B) Suppose the base in position 2 gets shifted to position 16; how will the sequence of 1,2,3 and 4 (above) be affected?
(C) If the base in position 6 is changed to a "T," how will the sequence of 1,2,3 and 4 (above) be affected?
III. LIFE! What does it mean?
In this case it means: Write a paragraph discussing A, B, and C.
(This activity is an adaptation of an activity developed by a colleague at Boulder High School, Richard Holland. Thanks for all your help!)
Genetic Code Activity
RNA Codes for Twenty Amino Acids
(Modified form the BSCS From Molecules to Man Teacher's Guide, p.41)
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