Kiwi DNA Extraction (Eric Blinder)

Kiwi DNA Extraction

Lesson Plan for 7th Grade Life Science

Monday - Friday 54 minute class period

Chapter 12 - DNA and Genetics

Principles Investigated: Students will be able to describe the appearance of extracted DNA from the kiwi. Students will be able to demonstrate the experiment through following directions and procedures. Students will be able to hypothesize how the DNA was isolated from the rest of the cell.

Video:

California Content Standards:

1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:

c. Students know the nucleus is the repository for genetic information in plant and animal cells.

2. A typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences. As a basis for under­ standing this concept:

e. Students know DNA (deoxyribonucleic acid) is the genetic material of living organisms and is located in the chromosomes of each cell. 7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will: c. Communicatethelogicalconnectionamonghypotheses,scienceconcepts,tests conducted, data collected, and conclusions drawn from the scientific evidence. e. Communicate the steps and results from an investigation in written reports and oral presentations.

Materials:

• graduated cylinder (50 mL)
• safety goggles
• 2 clear cups (plastic)
• kiwi fruit
• salt
• denatured alcohol (use caution)
• shampoo (clear in color, no conditioner)
• coffee filter
• pipette
• distilled water
• rubber band
• fork
• test tube
• knife

Procedure (students work in pairs):

1. Slice the kiwi into thin pieces ( 7 or 8 slices per fruit). Remove the skin.

2. Measure 30 mL of distilled water into a graduated cylinder and add it to a clear plastic cup.

3. Add the kiwi to the cup with the water.

4. Begin mashing the kiwi in the cup with a fork.

5. Add a pinch of salt to the kiwi and the water.

6. Add the shampoo to the solution. (Squeeze the shampoo bottle for about 5-10 seconds depending on the opening of the bottle. The desired amount of shampoo is about 10 mL.)

7. Continue mixing the solution, being careful not to mix so rough that the shampoo creates foam. Foam will make it slower to filter.

8. Prepare the other plastic cup with a coffee filter over the surface, secured with a rubber band. Push the filter inwards to create a cavity for the solution to sit.

9. Slowly and carefully, pour the "kiwi soup" over the filter. Allow the "soup" to filter into the cup for at least five minutes.

10. Using the graduated cylinder from step 1, measure 10 mL of denatured alcohol.

11. Pour the alcohol into a test tube. One student must hold the test tube for the rest of the experiment while the other student prepares the solution.

12. The student not holding the test tube should should remove the coffee filter and all of the sold material that did not filter. This may be thrown away.

13. The student not holding the test tube should now take the pipette and withdraw one pipette full of the filtered solution.

14. The student holding the pipette will slowly squeeze the pipette, releasing the contents of the "kiwi soup" into the test tube of denatured alcohol. (Be sure to remind the students to hold the test tube in a manner that does not conceal the tube itself. Recommend holding the test tube with two fingers. This will facilitate making observations.)

15. The resulting solution in the test tube will contain a coagulated, jelly-like layer of kiwi DNA that is visible to the unaided eye.

16. At this point, student can make observations and try to spool or hook the DNA around the end of the pipette. Students will be able to observe the thread-like structure of the DNA.

Student Prior Knowledge:

The students should already be familiar with the basic principles of cell science. Students should be aware that all eukaryotic cells contain a nucleus that holds the genetic material for that cell. DNA contains a set of "directions" for the cell and is located in the nucleus. Students should also be aware that the structure of DNA is similar to a long strand, and that during certain phases can tightly coil up around proteins or unwind and stretch out. Students should also be aware of the many applications of DNA extraction in genetic research and DNA fingerprinting.

Explanation:

All living things are made up of cells. All cells contain DNA. Therefore, under the proper conditions, DNA can be extracted from any living material. In this experiment, our goal is to purify the DNA from the plant cells in the kiwi fruit. In order to purify (or isolate) the DNA, we must get rid of everything else in the kiwi (all the organelles within the cell).

• The kiwi is mixed with water and is mashed with the fork in order to break apart large pieces of fruit and increase the surface area of the cells.
• The shampoo dissolves the fatty cell membranes.
• The salt causes the proteins and the carbohydrates to precipitate.
• The exposed DNA does not dissolve in alcohol and therefore coagulates to form a jelly-like substance that can be observed and manipulated in the test tube.
• Kiwi fruit is used because it naturally contains an enzyme that breaks down all of the extra proteins in the cell, leaving just the DNA.

Question and Answer:

1. What is actually in the solution in the pipette after it has been filtered?

Answer: Water, kiwi DNA, and a few extra cell parts (proteins) that fit through the filter. Mostly, this solution is made of water and kiwi DNA.

2. What is the purpose of each of the ingredient in the solution?

Answer: Fork - mash up the fruit to increase surface area; Salt- cause the proteins and carbohydrates to precipitate (separate); Shampoo- dissolves the membranes (nuclear and cellular); Alcohol - causes the exposed DNA to coagulate.

3. How can we use the DNA once we have isolated it?

Answer: DNA is used in many different applications. DNA fingerprinting can be used in forensic science and used to prove guilt or innocence in the court of law. DNA fingerprinting can also be used to identify genetic defects. DNA can also be taken out of one organism, manipulated, and placed into the cell of other organisms. This process can be done in order to express certain traits of an organism or in order to alter the function of a cell.

Applications to Everyday Life:

DNA extraction is the basis for the rapidly growing field of genetic engineering. Genetic engineering as well as the science of DNA is a relatively new field of study. The practical applications for DNA research are increasingly growing. Today, DNA fingerprinting is used to solve crimes to a degree of near certainty. The amount of genetic material needed to be recovered from a crime scene is so small that it may consist of a human hair. DNA fingerprinting technology is growing in efficiency and use and will be a viable career choice for students who are engaged in this type of activity. Other applications of purifying DNA include transgenic crop science and identifying genetic abnormalities. Transgenic crop science is a new field of study that may one day create crops that display the most desirable traits for harvest (disease resistance, size, shape, color, taste...).

References / Links:

http://www.daveansell.co.uk/?q=node/31

http://biotech.biology.arizona.edu/labs/DNA_Kiwifruit_teacher.html

http://www.york.ac.uk/res/sots/activities/diydna.htm