Lesson 10: Modeling Bacterial Transformation

Introduction:

There are many bacterial transformation labs already available. This lesson walks students through the process and lets them make a model of what happens in the bacteria itself. It is ideal for classrooms that do not have the time or money for all students to complete a transformation; however, you can certainly follow up with the actual wet-lab. This lesson is also recommended for academic Biology classes and classes with diverse learners including those with learning difficulties rather than advanced and AP Biology classes.

Learning outcomes:

Students will be able to describe the step of bacterial transformation as well as give examples where this process may be useful.

Curriculum alignment:

Biology Goal 3.04 – Applications of biotechnology with emphasis in the applications of transgenic organisms in restoration of the American Chestnut tree.

Classroom time required:

1 block class period: 45 minutes for modeling transformation including building bacteria model, 30 minutes for research of applications of transgenic organisms, 15 minutes to discuss applications.

Materials needed:

Per group of 2 students: 1 empty water bottle, 2 ft. yarn, 3 different colors of Velcro cut in 4 in. strips (each group needs 1 strip of each color), small adhesive dots (1 sheet per group), toothpicks, plastic lacing, 1 sandwich size Ziploc bag, 1 pair scissors, labels: Ice, Hot Water, Nutrient broth – 1 set per group, 1 sharpie, 1 bottle of white-out, copy of “Modeling Bacterial Transformation”, computer with internet connection For teacher demo: hot plate, Erlenmeyer flask, balloon, larger beaker of ice water, mitt for picking up hot flask.

Technology resources:

Computers with internet connection (per group of 2 students), Access to printer is also recommended to help students with research. Animations may be shown to the class as a whole with the aid of a data projector or Averkey connection to the television. If watching animation in smaller groups, earphones are recommended

Pre-Activities:

Students should already have knowledge of biotechnology terms such as PCR, restriction enzyme, clones, and sticky ends, as well as cell organelles, structure of the plasma membrane, DNA structure and process of replication, asexual reproduction.

Be sure that copies are prepared as instructed in the materials section.

Activities:

1. Review biotechnology concepts such as restriction enzymes, sticky ends, and BAC cloning. Inform students that bacteria are used further in biotechnology research in the production of transgenic organisms.
2. Give each group of 2 students a copy of “Modeling Bacterial Transformation.” Have one student read the opening paragraph aloud.
3. Direct students to look at the picture of the bacteria while you point out the different structures and review their functions.
4. Give each group the materials needed to build their model of a bacteria. Be sure to point out what each item is meant to represent. It may be helpful to have a model that you have completed in advance to show the students what it will look like.
5. Have a different student read the instructions for building the model aloud before students begin building.
6. Once students have completed their bacterial models, explain that each different color of Velcro represents DNA from a different source: one from the bacteria itself, one for antibiotic resistance (either from that bacteria or another), and one from a completely different organism. This third type of DNA is the “DNA of interest” and it is what we want to see change in the bacteria. It may mean making the bacterial colonies turn blue, produce a vaccine, etc. Remind students that in order for the DNA to have been cut, a restriction enzyme would have been used and in order to get the DNA to fit together, the cuts would have needed to produce sticky ends. Instruct students to put their Velcro pieces together to make a circle – this is their plasmid.
7. Explain that the plasmid and bacteria are now ready for transformation and show students the recombinant plasmid animation from the following web-site: http://www.dnalc.org/harlemdnalab/BacterialTrans.html It is not necessary to go through every animation on this site as it goes into detail for the specific “glowing gene” transformation lab. It does have lots of other great information if you would like your students to explore this later. It is used here as a preview of the process.
8. Distribute materials needed for transformation.
9. Have a student read procedure 1 and instruct students to follow the directions in bold type.
10. Have a different student read the information under procedure 2. Before students follow the directions in bold, perform the “Balloon in the flask” demonstration as follows: Place 10 mL of water in a 250-mL Erlenmeyer flask. Bring the water to boiling. Remove the flask from the source of heat and quickly and carefully place an empty balloon over the mouth of the flask. (It helps to blow up the balloons once before they are used.) Place the flask with the balloon on it into a large beaker of ice water. As the flask cools, the pressure differential between the outside and inside of the flask will cause the balloon to invert and line the inside walls of the flask. This will show how heat-shock forces the DNA into the bacterial cell. Now have students follow the directions in bold.
11. Have another student read the information under procedure three and have students follow the directions in bold.
12. Point out to students that the result of those three steps is a transformed bacteria. Read the final paragraph in this section and verbally or orally have students complete the concept check questions.
13. The final part of this lesson is to have students research applications of this technique. Have groups choose a topic from those provided on the list and use computers with internet connection to research their chosen topic. Allow a total of 30 minutes for instructions and research.
14. At the end of this time, allow each group to briefly describe what they found in their research. Groups waiting to tell about their topic should listen for similarities to their topic as well as how it may be different.

Assessment:

Allow verbal and/or written responses to the concept check questions at the end of the lesson. Check for understanding that the plasmid that students created contained DNA from an organism, other than a bacteria, by asking them to draw and describe the plasmid on the board. Listen for misconceptions, and quickly correct, during the discussion of transformation applications.

Modifications:

While this lesson can be presented to the entire class at once, students with hearing, sight, reading, or writing difficulties would benefit from being able to view the animations at their own pace. Working with another student also helps with organizing the discussion of findings for applications of transgenic organisms.

Alternative assessments:

Written responses to the assessment questions could be accepted for those students who have speech disorders or anxiety due to verbal assessments.

Supplemental information:

Extensions of this lesson include having students debate where GMO’s should be allowed in the food supply: plant, animal, or both.

Upon completion of the creation of a transgenic American Chestnut tree with fully functional blight resistant genes, trees could be released into the forest and given an opportunity to repopulate. This is the culminating step to the research being performed to restore the American Chestnut.

Critical vocabulary:

• Transformation: the genetic alteration of a cell resulting from the uptake, incorporation, and expression of DNA.
• Plasmid: an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently. In many cases, it is circular and double-stranded.
• Vector: a DNA molecule used as a vehicle to transfer foreign genetic material into another cell.
• Competent: the ability of a cell to take up extracellular ("naked") DNA from its environment.
• Transgenic: are organisms which have inserted DNA that originated in a different species.
• GMO: an organism whose genetic material has been altered using genetic engineering techniques. Some GMO’s do not contain DNA from other organisms, genes may just be removed or rearranged, and thus are not transgenic.
• Resistance: the capacity of an organism to defend itself against harmful environmental agents.
• Conjugation: the transfer of genetic material between bacteria through direct cell-to-cell contact
• Transduction: the process by which DNA is transferred from one bacterium to another by a virus