During this activity, by making beaded bracelets that represent the steps of translation, students simulate the creation of an amino acid chain. They are given an mRNA sequence that they translate into a corresponding polypeptide chain (beads). This activity focuses on the events and sites of translation. The activity provides students with a closer look at the process of translation, not focused solely on pairing codons with amino acids. The students move throughout the classroom, which simulates a nucleus, cytoplasm, a ribosome, and the A site, a P site, and an E site of a ribosome.
Translation is a difficult science concept for students and teachers. It is imperative to utilize manipulatives that clearly identify the process of translation. The activity we present here mirrors the cell’s process of translation by asking students to construct their own beaded bracelets.
While preparing my translation lesson, I (Dacey) searched for fun activities that allowed students to discover the process of protein synthesis (for an animation of this process, see http://www.youtube.com/watch?v=OabrAXr_9rg). The activities were designed to teach students how to read a messenger RNA (mRNA) codon sequence and match that codon up with an amino acid. I was not able to locate an interactive, artistic activity in which students simulate translation; therefore, I devised an activity in which students visit the different parts of a ribosome, perform the steps that build a polypeptide chain, and construct a fully functional protein.
This translation activity is based on “The Incredible Journey” (Higgins et al., 2009), an activity I learned about during a Project Wet workshop. During The Incredible Journey, students use large dice designed to teach students about the movement of a water droplet through the water cycle. With some modification, this activity can be adapted to lead students through the process of translation.
During translation, the ribosome decodes a strand of mRNA to produce a protein. After transcription, the mRNA transcript exits the nucleus of the cell and enters the cytoplasm. The transcript is now ready to undergo translation. Translation occurs in four steps: activation, initiation, elongation, and termination. During activation, an amino acid bonds to transfer RNA (tRNA). Initiation occurs when the ribosome binds the start codon in mRNA (AUG) with the amino acid methionine. Throughout the period of elongation, tRNA brings mRNA’s corresponding amino acid from the cytoplasm to the ribosome. This process of bringing in corresponding amino acids builds the growing polypeptide chain. Termination of translation occurs when a stop codon (UAA, UAG, or UGA) is reached in the mRNA sequence (Campbell & Reece, 2005).
Prior to beginning the activity, the instructor should review the locations in the cell where transcription and translation take place. Make sure that students understand the following before proceeding with the activity:
DNA is duplicated in the nucleus of a eukaryotic cell.
Transcription is the DNA-directed synthesis of RNA. RNA is made from a strand of DNA.
Translation occurs in the cytoplasm of a cell. mRNA moves out of the nucleus of the cell to a free ribosome in the cytoplasm to begin the process of protein synthesis.
The bases of RNA differ from those of DNA. The RNA template consists of uracil instead of thymine (found in DNA). Uracil from RNA pairs with adenine on the DNA template.
Quantities of 22 different beads; different colors and shapes work best. These can be found online or at a craft store (e.g., large jars of beads from Oriental Trading Company). Plastic pony beads work better than jewelry beads, and they are cheaper. Glow-in-the-dark beads or any other unique beads can be used for the START and STOP codons. The other 20 beads represent the amino acids.
String or leather for making bracelets. These can be found online or at a craft store (e.g., stretchy cording from Oriental Trading Company). Cut these into 20- to 25-cm lengths (Figure 1).
Copies of the dictionary of the genetic code (Figure 2; see http://www.bioscience.org/atlases/genecode/genecode.htm). I placed the genetic code from Figure 2 on a large piece of foam board and glued next to each code a representative bead (Figure 3). Once students located the amino acid, they quickly identified which bead represented that amino acid in the bracelet.
Strips of paper containing an mRNA sequence (see examples in Figure 4). One strip for each group of three students. I suggest using a large font.
Two signs labeled Nucleus or Cytoplasm. Signs labeled Ribosome, A Site, P Site, and E Site for each ribosome station.
Setting Up the Classroom
The “nucleus” is where all students will begin the activity with their mRNA transcripts. Place the Nucleus sign on a wall on one side of the room. Hang the Cytoplasm sign from the ceiling to show students that the remaining area of the room is the cytoplasm. Place the Ribosome, A Site, P Site, and E Site signs in stations around the room. Adjust the number of Ribosome stations to the number of groups in the class. Use painter’s tape on the floor to make a circle and label the area Ribosome. Creating several Ribosome stations can keep students from being overcrowded. Inside each Ribosome, place three small tables and label them A Site, P Site, and E Site. Place the beads, which represent the amino acids, and the genetic code (foam board) at Site A.
Designing the mRNA Sequences
Design one mRNA sequence for each group of students. See Figure 4 for examples. All the groups receive a different sequence; therefore, each group translates a different amino acid sequence for their bracelet. The mRNA sequences should contain at least 45 bases, or 15 triplet codes. Make sure that the mRNA sequences are divisible by 3. This ensures that the amino acids will correspond to the nucleotide triplets and a stop codon. Do not forget that translation will not stop coding until a STOP codon is read. Additionally, the mRNA sequence should be long enough for students to understand the process of translation and be able to simulate the process several times. When I did this with my students, I placed a STOP codon sequence in the middle of one or two of the mRNA sequences. This reinforces the idea that polypeptide chains have varying lengths and will assess whether students are able to recognize the STOP codon. Once students reach a stop codon, the polypeptide chain breaks away from the ribosome and folds into the specific protein for which their amino acid sequence coded.
Place students into groups of three and label them Student 1, Student 2, Student 3.
Have the groups meet at the nucleus.
Remind them of the process of transcription. SAY: In the nucleus an mRNA sequence is created from a DNA template. DO: Give each student group a strip of mRNA sequence. SAY: Once transcription is complete the mRNA exits the nucleus and moves into the cytoplasm. DO: Have students move to the cytoplasm and give each group a piece of string. They should tie a large knot on one end of the string. SAY: After the mRNA enters the cytoplasm it meets a ribosome and begins translation. DO: Give each student group one START codon bead (methionine). I use a glow-in-the-dark bead, and the students really like them. Tell them to place it on their string and that translation has now begun.
Student 1 stays in the cytoplasm.
Students 2 and 3 take the string with the START codon (methionine) and the mRNA sequence and move to the A Site.
At the A Site, Students 2 and 3 will find 21 different beads and a genetic code/bead chart (see materials). When the students arrive at the A Site, they translate the first three bases of their mRNA sequence and find the first corresponding amino acid. NOTE: Students should translate only one codon at a time.
After translating the three base pairs into an amino acid, Students 2 and 3 identify the correct bead and place it on their string. The bead represents the first amino acid of the growing polypeptide chain.
After adding the bead, Student 2 goes to the P Site with the string of beads and waits. Remind students that the P Site is the site where the growing polypeptide chain is made. Therefore, the string of beads will not leave the P Site during translation.
Student 3 proceeds to the E Site. The E Site is the exit site for the tRNA anticodon once it deposits its amino acid from the cytoplasm onto the growing polypeptide chain. After Student 3 exits the process, he/she returns to the cytoplasm. Remember: Student 2 should still be at the P Site. A diagram of student movement is shown in Figure 5.
Student 3 gives Student 1 the mRNA sequence.
Student 1 proceeds to the A Site of the ribosome.
Student 1 takes their group’s mRNA sequence to the A Site and translates the second codon into an amino acid.
Student 1 finds the corresponding bead for that amino acid, takes it to the P Site, and gives the bead to Student 2.
Student 2 adds the second bead to the string, or the growing polypeptide chain.
Student 2 leaves the P Site for the E Site so that he/she can exit translation and move to the cytoplasm.
Student 1 will remain at the P Site and hold the growing polypeptide chain.
Students repeat this sequence, taking turns at each station, until the codons have been translated into amino acids and they reach a STOP codon. Once a stop codon is reached, the growing polypeptide chain and tRNA molecule proceed to the E site. The polypeptide chain is released into the cytoplasm, where it folds into its corresponding protein.
The students move through the steps and act out the phases of translation. However, it is important to tell students that this is a simulation of how translation occurs. The translated codon does not exit, move back to the cytoplasm, and translate a new codon.
At the end of the activity, each group of students has a polypeptide chain that “translates” into a bracelet. Allow the groups to translate three different proteins so that each student has his or her own polypeptide bracelet (Figure 1).
Once the translation activity is complete, students will (1) have a better understanding of the process, (2) recognize the parts of the cell that are utilized during translation, (3) understand how to read the dictionary of the genetic code, and (4) be able to translate a codon into an amino acid.
When students enter the class, give them a card with one side of a DNA strand written on it and ask them to write in the complementary strand. Each student can then trade cards with another and check their partner’s strand. After they determine the complementary strand, have them fold the card over to cover the complementary DNA strand and write the mRNA strand that would be transcribed. During the activity, stop the students at the A Site and ask them to show me their translation of the polypeptide. After the activity, I ask students to fill out exit cards. I write an amino acid sequence on the board and ask students to determine the original DNA sequence. Although cells do not make DNA from proteins, students with a clear understanding of transcription and translation should be able to trace an amino acid sequence back to its original DNA sequence.
I do not introduce the process of translation on the same day as this activity. I introduce the processes of translation a class period before doing the activity. This activity is used as a formative assessment tool to determine how students understand the process through movement. I have found that the activity allows students an opportunity to further process their understanding of the physical process of translation. The first time I did the activity, I found that students were confused, so now I demonstrate the activity and provide them a copy of the directions. Additionally, I found that if I did each step with the students instead of letting them do the steps on their own, they were more likely to choose the correct amino acid.
Students enjoy making their bracelets and want to do the activity again. I see students in the hallway after class and they say they are wearing a protein or point to a red bead and say, “This is alanine.”
Incorporate mutations in the DNA sequence to further study the process of protein synthesis.
Incorporate a mutated transcript that would subsequently lead to the synthesis of a nonfunctional protein. Students could be organized into functional transcript groups and mutated transcript groups. Once the groups have followed the protein synthesis activity, the groups compare the resulting proteins and discuss how the healthy structures compare to the mutated products. After the additional activity, students research conditions that result from mutations in proteins such as Tay-Sachs disease and check-point proteins that regulate cell division. The use of check-point proteins may be used as an introduction to cell division and cancer.
Incorporate the Golgi apparatus so that when the student has completed construction of the protein, they move on to the Golgi for processing or folding. During this time, students tie their strings together to make their bracelets to represent the folding process. At the end of class, students have processed the protein, and when they walk out of class they are being exported from the cell.
Place some of the ribosome centers on endoplasmic reticulum (ER). Use painter’s tape to outline ER and the attached ribosomes. Providing visuals of different ribosomes allows students to see that translation takes place on free-roaming ribosomes and those attached to the ER.