7 DNA Transformation Results and Student Presentations
Following this lab, students will be able to:
- Plasmid Transformation into Bacteria
- Identify transformants
- Calculate transformation efficiency using your results
- Student Presentations
- Communicate results of an experiment you conducted to classmates
- Explain how different variables can affect the rates of:
- an enzyme-mediated reaction
- fermentation
- photosynthesis
- Results from DNA transformation. Describe growth (lawn, isolated colonies and number of colonies, or none). Do any colonies show green fluorescence? If so, how many and what fraction of the total show fluorescence? Are all the cells in a colony fluorescent, or do cells around the periphery look different in any way from cells in the center of the colony? Make sure you describe what you actually see and not what you expected.
| Without Plasmid | ||
| Arabinose | Ampicillin | Ampicillin + Arabinose |
| With Plasmid | ||
| Arabinose | Ampicillin | Ampicillin + Arabinose |
- Your score depends on your results. Did your results match your predictions for what would happen? If not, you can improve your score by identifying any plate which showed unexpected results and explaining why you might have gotten that unexpected result. Be specific about possible causes – an undefined “mistake” is not an adequate explanation. You must explain exactly what sort of mistake or other process might have led to the unexpected results you observed.
- Transformation efficiency: Observe your +plasmid amp plate and +plasmid amp+ara plate. Count the number of colonies you see on each plate, calculate the average, and estimate the transformation efficiency for your experiment by filling out the table and following the instructions below. Remember that each colony includes many thousands of bacteria but resulted from the growth and replication of a single bacterium.
| Plate | # Colonies |
|---|---|
| + plasmid ampicillin | |
| + plasmid ampicillin + arabinose |
|
| Average |
In this experiment, there was 0.157 µg of plasmid DNA per plate. Using this information and your average colony count, you can determine how many bacteria you transformed per microgram (µg) of plasmid DNA (how successful your transformation was). Use the equation below to calculate your transformation efficiency.
Transformation efficiency = Average # colonies on amp plates ÷ µg plasmid DNA on plate
Your Transformation efficiency is _________ units ____________
- What information can you derive from transformation efficiency values? How can knowing the transformation efficiency help you in planning future transformation experiments?
Student Presentations
Student groups will present on the experiment they conducted in either Week 3, 4, or 5. Guidelines for the student presentations are posted on Canvas and more information will be provided by your instructor.
