Properties of Strawberry and Banana DNA
To observe DNA from two
different sources and determine how the
physical properties of the DNA are similar. To understand the physical
nature of DNA.
Overview: In this lab you will
observe the physical properties of DNA. You
will break open strawberry and banana cells, prepare a filtered extract containing
strawberry and banana DNA, and separate out molecules of DNA in a test tube.
Grocery store strawberries are
a good source of DNA because they have 8 copies of each type of chromosome.
(This is called octoploid). You
will break open the cells of a strawberry, and then separate the DNA from the
remaining cell parts. You will
never be able to eat a strawberry again without thinking about how much DNA is
in it! After the lab, you may be able to take home a sample of pure
strawberry and/or banana DNA.
1. Label the diagram as discussed in class: cell membrane, nuclear membrane, DNA.
2. What type of charge does DNA have? How might that affect the way the DNA clumps together?
(per two students: each student will use either the strawberry or the
(per two students: each student will use either the strawberry or the banana)
and 1 slice of fresh banana
and beaker for holding test tube
Waste & Disposal:
(for each piece of fruit)
(for each piece of fruit)
Gently mash the bagged strawberry or banana for 2 minutes.
If not, followwaste & disposal
1. What substance in the extraction solution broke away the cell membrane?
2. What substance in the extraction solution broke away the nuclear membrane?
3. What substance in the extraction solution allowed the DNA molecules to come closer together?
4. What was the purpose of crushing the fruit?
5. DNA is soluble in water (will mix with water), but not in
What does this fact have to do with the method of extraction you used?
Explain what happened when the isopropyl alcohol came in contact with the
A person cannot see single cotton thread 100 feet away.
But if thousands of threads are wound together into a rope, the rope can
be seen at some distance. How is
this statement an analogy to the DNA extraction you did?
In order to study human genes, scientists must first extract the DNA from human
tissues. How would you expect the
method of DNA extraction for Human DNA to be the same as the method you used to
extract DNA from strawberries? How
would it be different?
Would the DNA be the same in any cell in the human body?
Hint: Remember that each person starts out as a single cell--the
If you wanted to extract DNA from a living person, what cells would you use and