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When we look at a living organism, including ourselves, we are seeing proteins or the results of proteins at work. DNA is the instructions in the cell to make these proteins, and as a result it determines nearly everything about us including our eye color, hair color, and hair texture. It determines how the cell functions by ordering the production of enzymes, receptor proteins, and other important proteins. By adding or changing a DNA sequence, we can directly influence the traits of the organism because this new DNA will be used to produce a protein that was not previously produced by the organism. Because DNA is such an important molecule, it is essential to understand how it is used to carry information and produce proteins.
In this activity, students will work in groups of three or four to model protein synthesis. Genes, sections of DNA that code for a protein, will be located in a central location in the room, which will be considered the “nucleus”. The tRNA cards will be located at the group’s workspace, which will serve as the “ribosome”. One group member will go to the nucleus and select a “gene” to transcribe. When finished, the student will take the mRNA back to the ribosome where the group will translate the mRNA strand.
Disciplinary Core Ideas
Science and Engineering Practices
Length of Time for Classroom Teaching
Activity 1: Transcription – 30 minutes
Activity 2: Designer DNA – Genetic Engineering -10 minutes
Preparation Procedure
Print out the DNA Sentence Strips, tRNA cards; 1 set for each group, have blank strips to transcribe mRNA; 1 for each sentence to be transcribed. Print enough copied of the Decoding DNA Student Handout and have the Decoding DNA PowerPoint ready.
Instructions
This lab has two activities; Transcription and Designer DNA – Genetic Engineering. Hand out the Decoding DNA Student Handout. The handout includes the instructions for the transcription activity. In addition, the handout provides places for students to write down their sentences for both activities, and also includes reflection and conclusion, as well as assessment questions.
Proteins are polymers of amino acids, produced in the cell by structures called “ribosomes”. There are 20 different amino acids that are analogous to letters in the alphabet. We have only 26 letters in our alphabet, but they can be ordered and rearranged to produce thousands of words and a near-infinite number of sentences. Amino acids work similarly in making proteins, where the order and arrangement of these amino acids determines the function of the protein.
DNA is a polymer of four different nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C). It is arranged in long chains that form a double helix. On each side of the helix is a complementary, matching, nucleotide. Adenine (A) always pairs with thymine (T), while cytosine (C) always pairs with guanine (G). This enables DNA to replicate, or copy itself, by “unzipping” and adding complementary nucleotides to each single strand. This allows new cells to be produced with identical copies of the DNA found in the original cell.
Transcription: DNA to mRNA
In plant and animal cells, DNA stays in the nucleus. The instructions in DNA need to be copied into another molecule, RNA, to be carried to the ribosomes where they can be read to make proteins. RNA is another polymer of four nucleotides very similar to DNA. The only nucleotide that is different from those in DNA is uracil (U), which replaces thymine and complements adenine. mRNA is only a single strand that can leave the nucleus and be used by ribosomes as a recipe for making the protein. mRNA is produced in the nucleus in a process called “transcription”. The DNA strand is separated and the enzyme RNA polymerase adds complementary nucleotides to build a matching mRNA strand.
After the mRNA molecule is transcribed, it can leave the nucleus and move out into the cell where the ribosomes can translate the RNA into a protein.
Translation
Translation is the production of a protein from an mRNA strand by a ribosome. During translation, a ribosome uses tRNA molecules to determine the order of amino acids. The tRNA reads sections of mRNA three nucleotides at a time. These three nucleotide sections are called “codons”, and they are complemented by an anticodon on the tRNA molecule. AUG is the “Start” codon. Translation is divided into three parts: initiation, elongation, and termination.
Initiation
A tRNA molecule attaches to the “Start” codon, AUG. This allows a ribosome to attach to the mRNA.
Elongation
The ribosome continues to match antocodons to codons and add amino acids to the protein.
Termination
Occurs when a “Stop” codon is reached. The mRNA, ribosome, tRNA, and protein are all released. The protein folds into its shape and starts to work in the cell. The other components can be reused to make the protein again.
Introduce the topic and assess students for prior understanding.
Activity 1: Transcription- 30 Minutes
Instructions Hand out the Decoding DNA Student Handout. The handout includes the instructions below and places to write down their sentences.
Translation Instructions
Sentence # ___ ______________________________________________________________ Sentence # ___ ______________________________________________________________ Sentence # ___ ______________________________________________________________ Sentence # ___ ______________________________________________________________
Activity 2: Designer DNA – Genetic Engineering (5-10 minutes)
Overview With the development of new technologies, such as CRISPR, DNA can be edited more easily inside living cells. This means scientists can design a protein and construct a DNA sequence that will code for that protein. These proteins are made up of the same building blocks as all other proteins, but they can introduce new traits to an organism.
Sentence for students to engineer: Biotechnology can improve our quality of life.
3D Printer STL File
3D Printer Ribosome Model STL file
Additional Resources
Discuss with the students the questions on their handout. Students should understand the processes involved in producing proteins as well as how inserting engineered DNA can enable organisms to produce proteins that are new to that organism.
To learn more about agriculture careers visit https://agexplorer.ffa.org/.
Any educator electing to perform demonstrations is expected to follow NSTA Minimum Safety Practices and Regulations for Demonstrations, Experiments, and Workshops, which are available at https://static.nsta.org/pdfs/MinimumSafetyPracticesAndRegulations.pdf, as well as all school policies and rules and all state and federal laws, regulations, codes and professional standards. Educators are responsible for abiding appropriate legal standards and better professional practices under a duty of care to make laboratories and demonstrations in and out of the classroom as safe as possible. If in doubt, do not perform the demonstrations.
Investing in Kansas teachers and students is a priority for the Kansas Corn Commission. We are committed to providing materials and training to support STEM education while fostering an understanding of how corn farming and agriculture fit into our daily lives. Professional development workshops are offered to teachers seeking to expand their knowledge and inquiry-based teaching skills. Workshop participants receive free lab supplies needed for the lessons.
This lesson is the work product of the Kansas Corn Commission. Our lessons are written in collaboration with Kansas teachers for use in the classroom. Teachers may copy and share this curriculum. Use of this product for commercial or promotional use is prohibited without express permission of Kansas Corn.
As the need to produce more food with less resources grows, it is important that future generations have a better understanding of agriculture and how corn farming and agriculture fit into our daily lives. That’s why the Kansas Corn STEM program provides lessons to teach science through the lens of corn. We are committed to providing free materials and training to support educators.
