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. |
