DNA
Today you will
extract DNA from some of your cells and learn more about DNA.
Extracting DNA from Your Cells
Cells from the lining
of your mouth come loose easily, so you will be able to collect cells
containing your DNA by swishing a liquid around in your mouth.
To extract DNA from
your cells, you will need to separate the DNA from the other types of
biological molecules in your cells. You
will be using the same basic steps that biologists use when they extract DNA
(e.g. to clone DNA or to make a DNA fingerprint). You will follow these 3 easy steps to extract
the DNA:
Detergent
eNzymes (meat tenderizer)
Alcohol
Getting
Your Sample of Cells
Obtain
a cup with sports drink. You will need
to get thousands of your cheek cells in the sports drink in order to extract
enough DNA to see. Therefore you should swish
the sports drink around in your mouth vigorously for at least one minute. Then
spit the drink back into the cup.
Step 1: Detergent
Open
the centrifuge tube (place the lid on a paper towel. Why is this important?) Add a small amount of
detergent to a centrifuge tube (about 0.25 mL).
Now carefully pour the drink containing your cheek cells into the test
tube with detergent until the tube is half
full.
Step 2: Enzymes
Add a pinch of enzyme
(meat tenderizer) to your centrifuge tube.
Replace the lid on the tube; gently invert the tube five times to
mix. Place the tube in the test tube
rack. Let the mixture sit for at least
10 minutes. While you are waiting, answer the questions on the following pages.
Why am I adding
detergent?
Why am I adding
enzymes?
The protease in meat
tenderizer comes from plants, but animals also make proteases. What is one reason why humans and other animals
need to have protein-cutting enzymes?
DNA
Structure
DNA consists of two
strands of nucleotides wound
together in a spiral called a double
helix. Read the explanation in the
figure before answering questions 1 and 2.
(Figure from Biology
-- A Guide to the Natural World by Krogh)
1. The three components of each nucleotide are:
______________________
______________________
______________________
Draw a rectangle
around a single nucleotide in the double helix.
2. The complete name for DNA is deoxyribonucleic acid. Which component of each nucleotide accounts
for the "deoxyribo” part of this name?
3. DNA has the same double helix structure in
all living organisms. However, we know
that a plant, mammal and bacterium must have different genes in their DNA to
result in the very different characteristics of these different organisms. So,
the question is: What is different in the DNA of these different
organisms? Complete the
following table to identify what is different between the DNA of the plant,
mammal and bacterium.
|
|
Compare the plant
and mammal DNA.
|
Compare the mammal
and bacterium DNA.
|
|
|
|
|
|
|
|
|
|
|
|
|
In your attempt to
analyze DNA samples from three different species, what claims can you make
about the similarities and differences of the DNA samples?
Step 3: Alcohol
Using a pipette,
slowly add cold rubbing alcohol into the test tube; let the alcohol run down
the side of the test tube so it forms a layer on top of the soapy liquid. Add
alcohol until you have about 2 cm of alcohol in the tube. Alcohol is less dense than water, so it
floats on top. Do not mix or bump the test tube for 10 minutes. DNA molecules will clump together where
the soapy water below meets the cold alcohol above, and you will be able to see
these clumps of DNA as white strands.
Why doesn’t the
alcohol mix with the water?
No comments:
Post a Comment