Lesson 1 – Scientists Prepare and Plan
Course: Biology, Genetics, Biotechnology, Environmental Science
Unit: Genetics and Heredity
- Observations lead to hypotheses and experimental design.
- Halobacterium (Halo) respond to changes in their environment, such as the amount of light.
- Students use scientific thinking to consider how the environment impacts gene expression and cellular networks.
- Students conduct research into current Halobacterium observations and make a list of possible variables (which leads to lesson 2).
Instructional Activities: (One 50-min period, with a bit of homework if needed)
Students should complete these lessons near the end of a genetics unit. Typically students would have learned that organisms (and individual cells of multicellular organisms) respond to their environment by changing which proteins they make. A major way they do this is by regulating ”gene expression” through control of transcription. Some genes are “turned on” to make mRNA for their corresponding protein, and some genes are “turned off” to stop making mRNA for their corresponding protein. This allows the cell to conserve energy by producing only what is needed at that time.
This is usually studied in high school classrooms in a fairly artificial situation. E. coli bacteria are transformed by adding plasmid DNA, and their environment is changed with the addition of the molecule arabinose. The gene for green fluorescent protein (GFP) is “turned on” (transcribed) in the presence of arabinose and “turned off” (not transcribed) in the absence of arabinose. This serves as a good model system to study these processes, but E. coli bacteria in nature do not have the gene for GFP, and they do not respond to the molecule arabinose in this manner.
To study this in a more natural situation where an organism’s DNA is not altered, we will use the model system of Halobacterium (Halo), which lives in high salt environments such as the Great Salt Lake. This module will give students a way to act as scientists as they study how this organism responds to changes that occur in its natural environment. They will use networks as part of their experimental process in the same way scientists use networks to hypothesize, model, and predict cellular responses to environmental cues.