04.22.2016
Written By: Ralm Ricarte
What’s up world,
Today’s lesson was an introduction to cell biology and DNA. The intro presentation, which was stuffed with very pretty images of cells, focused on three principles:
- Cells, tiny little compartments that have distinct responsibilities for keeping something alive, are the basic building blocks of all living things.
- A cell’s shape is related to its function.
- DNA is the instruction manual for building and maintaining each cell.
The students, who had some prior knowledge of cell biology, were interested and engaged with the presentation.
The experiments were split into two sections. In the first section, the students use optical microscopes to look at slices of a red onion and a mouse brain. For the red onion, the cells are large enough to see with a microscope. Some red onion slices were stained with methylene blue so that the cell nuclei could be seen. For the mouse brain, the cells are too small to be seen with the microscopes. This contrast between the two samples was supposed to emphasize that cell shape and size can greatly vary among species. The students, however, didn’t really seem to appreciate or understand the difference. This section should be redesigned to make the microscope samples more interesting to the students.
In the second section, the students extracted DNA from strawberries, banana slices, or red onions. The choice of vegetable or fruit served as the variable in this experiment. The process for extracting the DNA is listed below. After the students filtered the extract solutions, we showed them that the extracted solutions with DNA scatter red laser light more intensely than the extract solution alone. This phenomenon, first introduced to the students in the Light Day 2 experiments, indicates that the solution contains a higher concentration of a solute (in this case, DNA). The students then precipitated the DNA by adding cold rubbing alcohol to the solution. Those who used a strawberry recovered a lot of DNA (the precipitate was thick and white), while the ones who used a banana slice or red onion saw less DNA. Some students used the optical microscopes to look at the extracted DNA, though the DNA is much too small to see the double helix structure. Due to the simplicity and messiness of the experiment, the students really enjoyed this section. Next time, we should prepare a strawberry slice to look at under a microscope.
See ya,
Ralm Ricarte