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What is DNA? DNA Extraction from Kiwifruit

From Biotech Project, University of Arizona and the Office of Biotechnology, Iowa State University
Modified by: Kirstin Bittel and Rachel Hughes



Time: 1 class period
Preparation Time: 5 minutes coping lab protocol for each group
5-10 minutes setting up materials
Materials: Teacher Guide / Student Guide
Knife for cutting kiwi
One small Ziploc bag per group of students
Jar or beaker that fits strainer or funnel
Strainer or funnel
Cheese cloth (or a #6 coffee filter)
Ice water bath (a large mixing bowl works well)
Water
Clear-colored shampoo, such as Suave Daily Clarifying Shampoo
Kiwifruit, half a kiwi per group of students
Table salt, either iodized or non-iodized
1 large test tube (holds 20 ml) per group, preferably with a cap
1 small test tube (holds 10 ml) for each student, preferably with a cap
Cold 95% ethanol (grain alcohol)

 


Abstract
During this lesson students will be introduce to DNA spooling as a means to identify the role of the gene.

Purpose – Engagement of students in isolating and extracting DNA from kiwi cell.

Objectives
Students will be able to:-
1. Isolate DNA from kiwi cells
2. Spool the DNA from a kiwi
3. Describe the role of the DNA and genes
4. Explain how knowledge of DNA and genes can be used in genetically modifying foods


National Science Education Standards
Content Area C – The Cell
- Cells have particular structures that underlie their functions. Every cell is surrounded by a membrane that separates it from the outside world. Inside the cell is a concentrated mixture of thousands of different molecules which form a variety of specialized structures that carry out such cell functions as energy production, transport of molecules, waste disposal, synthesis of new molecules, and the storage of genetic material.

- Cells store and use information to guide their functions. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires.

Teacher Background
DNA is in the cells of all living organisms. DNA is essentially the blueprint for an organism. It encodes genetic information in the nucleus of cells. It determines the structure, function and behavior of the cell/organism.


Related and Resource Websites

http://biotech.biology.arizona.edu/
http://www.biotech.iastate.edu/

 

 

Teacher Preparation
Make up the extraction solution ahead of time.
Extraction solution recipe:
For one liter of the extraction solution, mix 100 ml of shampoo (e.g. Suave Daily Clarifying Shampoo- many shampoos will work, but do not use shampoos with conditioner or baby shampoo) and 15 g of table salt (iodized or non-iodized will work). Add water to make a final volume of 1 liter. Dissolve the salt by stirring slowly to avoid foaming. Measure 20 ml of solution for each pair of students.

Activity
Engage (What are genes and what they have to do with Genetically Modified Foods?)
As students enter room, have the following questions on the board/overhead.

1) One way to purify a molecule is to get rid of everything but he molecule. Thinking back to your studies on the cell, if we want to isolate the DNA from kiwifruit, what do we need to get rid of?
2) What materials would you use to do that?
3) What can we do with the DNA once we have purified it?

Allow students a few minutes to reflect and write about these questions in notebook. Then share thoughts with the class. Possible answers are listed below.

1) All parts of the cell besides the DNA, i.e. cell wall (kiwi is a plant, after all), cell membrane, mitochondria, Golgi apparatus, endoplasmic reticulum, vacuoles, lysosomes, nuclear membrane, etc.
2) Something to mush the cells (blender or your hands), something to destroy membranes (soap dissolves them), something to get rid of proteins and carbohydrates (salt causes them to precipitate), something to separate insoluble cell stuff from soluble DNA, and something to help get the DNA (alcohol precipitates it).
3) Use it in DNA fingerprinting (solve a crime, see a genetic defect), put it into another organism to give it specific traits (this is called transformation or genetic engineering), other?

Tell students, “Using the information that you have come up with, we will look into a kiwifruit to see if we can figure out just how genes and DNA are related to Genetically Modified Foods. First, we need to extract the DNA from these kiwifruits. In pairs, you will follow the procedures provided.

Allow students time to follow the procedures to extract the kiwi DNA. As students work, it is advisable to walk the room overseeing procedures and discussing what students are seeing.

Bring the class back together after the DNA has been extracted. Ask them to explain the steps they went through and the results of each step. What did they notice? What did they wonder about?

Ask them, “Now that you have seen what kiwifruit DNA actually looks like, how can we use this to help us genetically modify food?”

Allow time for discussion and accept all responses that are reasonable and record them on the board.

Homework
Look around your house. What foods might be genetically modified? How could we test to find out?

Embedded Assessment

This is an opportunity to assess students practical lab skills, how well they collaborate in groups, and their ability to follow formal protocol.
 


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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Supported by NIEHS grant # ES06694


1996-2007, The University of Arizona
Last update: November 10, 2009
  Page Content: Rachel Hughes
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