Mystery Yeast Mutation

In Fall 2002, a group of high school students participated in an after school program on genetics. We performed the investigation "Mystery Yeast Mutation" designed by the Genetics Science Learning Center at the University of Utah. Instructions for the experiment are available on line. During the colloquy we ran out of time to complete the investigation so we posted photos of the yeast cultures for the students to view at home. We will keep these photos online for teachers and students who do not have access to the necessary materials.

Review:

We started with an unknown yeast that exhibited some curious behavior. The yeast would grown on the YEAD plates but not on the MV plates. Some of the hypothesis we came up with included:

• MV plates contained a poison
• YEAD plates contained food for the yeast
• MV plates contained a virus or bacteria that killed the yeast
• the yeast was sick or had a mutation that kept it from growing on the MV plates

Experiment

To discover the reason the yeast only grew under some conditions you were given the following tools:

• MV and YEAD plates
• Adenin, Cytosine, Thymine and Guanine disks
• Unknown yeast
• Baker's yeast

Each group then chose a line of investigation to determine why the yeast only grows on YEAD plates.

Results

The yeast were stored for 4 days in the dark at room temperature. They were then moved to a refrigerator to stop the yeast from multiplying.

View photos of the plates (link will open in a new window)

Since there were many repeats I took a typical example for each combination. If there were any anomalies I took multiple photos.

Conclusions

After you have examined the photos, re-evaluate your hypothesis. Email your conclusions or further questions to the instructor.

Good Luck!