Model the central dogma of molecular biology by constructing a colorful chain using a simple code (and some delicious cereal).
COVID-19 Learning Note: Viruses hijack the cells of the organisms they infect to make more viruses. The genetic code of coronaviruses is stored in RNA that is directly translated into viral proteins by the host cells they infect. In the model used in this Snack, that would be akin to sneaking into the room with your own sheet of paper and making a designer cereal chain for yourself.
- Make up a template for the cereal chain using single letters to correspond to different colors of cereal—for example, yellow, orange, purple, purple, red, red, green, yellow, yellow, orange, purple would be YOPPRRGYYOP. Write the template on a piece of paper.
- Tape your template down on a table in the corner of the room so no one can remove the template. Place some string on the floor near the table to section off the area.
- Arrange paper and pencils next to the template.
- Place a cup of cereal and some chenille stems in the main part of the room.
Tell people that the instructions to make their cereal chain are in the corner of the room. Since the template is taped down, they can use the paper and pencils to help them remember the order.
Direct people to construct their cereal chains in the main part of the room using the cereal and chenille stems.
Compare the finished cereal chains. Is everyone’s the same?
The process of making the cereal chains models the process of how proteins are made in a cell. The initial template represents a single copy of DNA that sits in the nucleus of a cell and gives instructions for how proteins are made. In order to get this information to an area where proteins can be made, it must be copied into RNA. RNA is very similar to DNA, but has a different form: this is represented by the handwritten notes.
The copying process is called transcription. Just like in a cell, a single DNA template gave rise to many RNA transcripts. In a cell, these transcripts move from the nucleus of the cell into the cytoplasm. The string you used to section off your instruction table represents the nuclear membrane that holds the DNA in the nucleus of a cell.
In the cytoplasm, a process called translation occurs: ribosomes use the RNA transcripts to assemble proteins from amino acid subunits. In cells, the genetic code dictates which amino acid residues correspond to a given DNA sequence. In the cereal chain, the letters in the instructions correspond to the color of the cereal.
How did the different cereal chains compare? It’s likely that most were identical, since they were all generated from the same initial instructions. However, sometimes a difference can arise due to an error in copying or an error in making the chain. This part of the model extends to what happens in cells where there are also sometimes errors in transcription or translation.
The cereal chain represents a model of a string of amino acids. In a cell, this amino acid chain would then be folded into a three-dimensional protein. This folding can be modeled with simple rules like “yellow always links to yellow” or “orange avoids green” to give an idea of how chemical rules such as disulfide bridges and hydrophobic interactions dictate the final form of a protein.