Lesson Plan 15
Biology
Shawn P. Schwartz
30 Students
OBJECTIVE:
Students will visualize how DNA is extracted from cells by performing a simple laboratory experiment. Students will then use this knowledge to further understand how scientists are using DNA extraction to try to clone human cells, and to predict what some of the social and moral implications would be if human cloning were successful.
MATERIALS:
-Spiral notebook
-Pen/Pencil
-Laboratory room
-Safety goggles
-Laboratory experiment handout
-A source of DNA (three stalks of broccoli)
-Meat tenderizer to be used as a restriction enzyme
-Salt
-Water source
-Three strainers
-Three beakers
-Three stirring rods
-Three blenders
-Three test tubes
-Detergent
-Rubbing alcohol
-Personal computer
-Projector
NOTES:
The students will be performing a laboratory experience that may not be very dangerous but has the potential to be very messy. Although the students are usually well behaved, I may need to monitor them to make sure that they stay on task, always wear their safety goggles, do not play with any of the other chemicals or devices in the laboratory, and put the lid on the blender when using it to blend the materials. These steps are necessary to enforce the safety standards within the laboratory.
STEPS:
ANITICIPATORY SET: (2 minutes) Ask the students to visualize a world where human cloning has been perfected. What are some of the scientific advances of this society?
1. (8 minutes) Take class attendance, divide students into three groups of ten, make sure every student has the copy of the laboratory experiment handout given to them the previous day, and walk to the biology laboratory room.
2. (10 minutes) Have each of the three groups place one stalk of broccoli, a pinch of salt, and 200 mL of water into the blender. Make sure they secure the lid to the blender and blend the materials for 15 seconds. Have the groups pour the mixture through a strainer into a beaker. Then have the groups add 75mL of detergent to the strained mixture and mix it slowly for one minute.
3. (10 minutes) Have each of the three groups pour the mixture into the test tubes and fill each about one third of the way full. Then have the students add a pinch of meat tenderizer and gently stir the mixture. Explain that if they stir too roughly, they will break up the DNA strands and make the extraction more difficult to see. Next, have the students tilt the container and pour an equal volume of rubbing alcohol down the side of the test tube to form a layer of alcohol on top of the mixture. Make sure the students pour down the side of the test tube to form a layer on top of the mixture instead of mixing the rubbing alcohol into it.
4. (5 minutes) While the DNA is materializing, explain to the students that each broccoli cell is surrounded by a cell membrane. The DNA is stored within this membrane, so the students removed the membrane by adding detergent. Because the detergent destroys the cell membrane, the DNA is able to move freely within the liquid mixture. Although the DNA is no longer protected by the cell membrane, it is still protected by proteins. The meat tenderizer contains enzymes that are able to cut away the proteins to further expose the DNA. When the alcohol is added, the protein and other parts of the cell remain in the mixture layer, but the DNA rises into the alcohol layer. Eventually, white stringy material that looks like snot can be collected on a stirring rod. This is the DNA, which is necessary to form a stalk of broccoli.
5. (5 minutes) Have each of the three groups use a stirring rod to pull the DNA out of the mixture by carefully swirling the stick between the layer of rubbing alcohol and the broccoli mixture. Explain to the students that this is the broccoli’s DNA.
6. (20 minutes) Lead a class discussion regarding the social and moral implications of DNA extraction. Explain that the cloning of organisms such as sheep and even humans relies upon the extraction of DNA. Use my personal computer and the projector hooked up to it to show students how to navigate to http://www.detnews.com/2003/nation/0304/11/a12-134341.htm by going to the Hip Hop Circuit website and clicking on Resources, then Writing Tools, then The Detroit News, and finally asking them to type, “sheep cloning” into the search engine and click on “Human Cloning Hits ‘Pothole’” in the search results. Call on individual students randomly to each read aloud one paragraph of the article. After the article is read, explain to the students that they will be writing a three hundred-word, fictional article about how they think society would be affected if human cloning was possible. Also, require that the students mention in their articles a few human rights groups that they think might be in favor of or opposed to human cloning. Finish the lesson by having the students clean up their laboratory experiments before the bell rings.
FOLLOW-UP ACTIVITY:
Students will write a three hundred-word, fictional article about how they think society would be affected if human cloning was possible as well as what human rights groups they think might be in favor of or opposed to human cloning. This activity will allow students to directly tie in the aspect of social justice into their laboratory experiment involving DNA extraction by making them think of how the cloning of organisms can benefit or harm society as a whole. Students will be assessed by whether their articles meet the guidelines of the assignment. If the students’ essays meet the criteria of being three hundred-words long, using proper sentence structure and development, as well as demonstrating original thought, then their assignments will receive an “A”.
LITERACY ASPECT:
In this lesson a few students will utilize their reading skills by reading aloud one paragraph in the article titled, “Human Cloning Hits ‘Pothole’”. All students will make use of their reading skills by following along while reading this article. Students will also be required to use their reading skills by following the directions of the experiment listed on the laboratory experiment handout. Finally, as a homework assignment, every student will develop their writing skills by writing a three hundred-word article about how they think society would be affected if human cloning was possible as well as what human rights groups they think might be in favor of or opposed to human cloning.
REFLECTION/RESPONSE:
The students paid attention to the subject matter because of the usage of a variety of audiovisuals to teach them as well as the hands-on activity of a laboratory experiment involving DNA extraction. However, this lesson not only takes a great amount of preparation, but it also takes a great deal of clean up. Make sure that the students prepare for the lab by reading the laboratory experiment handout the night before and make sure that the students have an ample amount of time to clean up laboratory after explaining their homework assignment.