Isolation of DNA
Author(s): Lola Berber-Jimenez, Jenny Bush
Subject: Life Science
Grade Level(s): Grade 8
Big Idea(s): DNA is present in the cells of all living organisms. This procedure is designed to extract DNA from kiwi in sufficient quantity to be seen and spooled. This activity is ideal for students to work in pairs, but each student will have a tube of DNA at the end.
What you need: ziplock bags (1 per student pair)
jar or beaker that fits strainer or funnel (1 per 10 students)
strainer or funnel (1 per 10 students)
cheese cloth (cut to cover the funnel)
ice water bath (1 per 4-6 students; large mixing bowl works well)
kiwi fruit (6 pieces per student pair)
extraction solution (1 tube of 20 ml per student pair): see Instructor’s Page for preparation
cold 95% ethanol or isopropanol (2-3 ml per student)
small test tubes (1 per student)
toothpicks, wood pencil, or glass stirring rod (1 per student)
Setting: Classroom
Time Needed: about 30 minutes
Summary:
DNA is present in the cells of all living organisms. This procedure is designed to extract DNA from kiwi in sufficient quantity to be seen and spooled.
Learning Goals / Objectives:
1. DNA is in all living things.
2. DNA can be removed and isolated from a living substance.
Setup:
See attached Instructor’s Notes.
Anticipatory Set:
Ask students “What is DNA?” and ask them to draw or write down what they think DNA is.
Instructions / Activities:
- Get 6 pieces of kiwi and put them in a ziplock bag.
- Add 20 ml of extraction solution to the ziplock bag. Make sure the bag is closed without much extra air.
- Mush the kiwi throughly but carefully so the bag doesn’t break, for about 5 minutes. What does mushing the kiwi do?
- Cool the kiwi mixture in the ice bath for a minute. Then mush the kiwi more. Cool, then mush. Repeat this several times. Why do we cool the mixture?
- Filter the mixture through cheesecloth. All the groups can combine their mixtures at this point, to filter together. What is being filtered out? What is going through the filter?
- Add approximately 2 ml of kiwi solution into each test tube, one for each student.
- Being careful not to shake the tubes, add approximately 2 ml of cold 95% ethanol to each tube. What do you think the ethanol does? Why do we want it cold?
- Take a look at your tube. What do you see in the top portion of the liquid? You can actually pick up the DNA at this point, using a toothpick, wood pencil, or glass stirring rod.
Assessment:
See attached Student Data Page.
Wrap-up / Closure:
All materials may be disposed of in regular trah cans or in sinks.
Check out this video of extraction of DNA from strawberry.
http://genetics.thetech.org/online-exhibits/do-it-yourself-strawberry-dna
Tags: Grade 8
Categories: Life Science