For High School Teachers
 
 
  From DNA to Organism: A Study in DNA Function for the High School Biology Classroom
 
 

Module 4: Yeast and the gene

Teacher suggestions for Module4:Quantitative analysis

     Timing

  • 1 period for prelab and setup
  • 1 period for data collection and postlab 1– 3 days later

 

     What you need to set up

  • Spectrophotometer (or other cell counter)
  • Cuvettes and racks
  • Incubator at 37 °C
  • Yeast culture stock (wild type and AKT-1 mutant)
  • High K+ media
  • Low K+ media
  • Water
  • 3 X 100– 1000ml pipettes

 

     What the students need

  • ______ ml of each yeast culture sample (Wild type, AKT-1 mutant)
  • 4 X cuvette for spectrophotometer
  • Low K+ media for yeast
  • High K+ media for yeast
     PreLab 15 minutes

         To prepare the students for this part of the lab module, they need to be familiar with the idea of a transgenic organism, specifically yeast. Introduce the idea that the gene they have been working with, from the plant, has been inserted into a yeast cell to attempt to determine what the gene will do. The yeast have had their own potassium channels removed so that they will not interfere with our results. This is information that the students do not need but might help some of the more inquisitive ones to understand.

         The main goal of this activity is to familiarize students with one way to determine gene function but also to introduce them to methods for culturing microorganisms. It is a good idea to stress the importance of good lab protocol (including labeling your samples!). During the prelab it would also be helpful to explain the idea of optical density as a measure of microbe culture growth. For many students this may also be their first introduction to the spectrophotometer (or other cell culture counter), so some time would be well spent explaining how it works (See attached PowerPoint presentation, see above file for how it works).   

     Lab 30-40 minutes day of experiment, 20-30 minutes to check data

                 The setup of the lab will not take too long for the students as they are just collecting their samples and various liquid growth media. They have the protocol to follow and should be able to do so without too much trouble. The number and arrangement of the spectrophotometers will be the limiting factor both here, to observe and record the starting OD (optical density, a way to measure concentration of yeast by quantifying the extent to which the yeast culture absorbs light passing through it; a high OD will indicate a dense concentration of yeast) and in the final data collection. 

 

PostLab 5 minutes clean up, 20-30 minutes

            During the post lab, it would be wise to set up a data table on the board and have all the groups add their data to it. This not only gives the students a better idea of what happened but also sheds some light on any odd data points that may come up. The discussion can include what happened, what it means, and what went wrong if anything.  

 

     Homework

           The lab report is the homework for this activity.