Download 1 DNA Extraction Lab Page. Name Date DNA Extraction Lab Period

DNA Extraction Lab Page.
Name
Date
DNA Extraction Lab
Period
1
Introduction:
DNA contains the genetic information that determines an organism’s traits. The traits are
passed down from one generation to the next. DNA is contained within the nucleus of almost
every cell in the human body.
The length of DNA in a cell is about 100,000 times as long as the cell itself but only takes
up about 10% of the cell’s volume. This is because DNA is specially packaged. The basic
structure of DNA is that of a twisted ladder called a double helix. To make the DNA molecule
more compact, the DNA wraps itself around proteins, called histones. A segment of the DNA
wrapped around a histone forms a nucleosome. A chromosome is made up of many nucleosomes
in a row. If the 46 chromosomes in a human were lined up, they would measure about six feet
long.
When chromosomal DNA is extracted from multiple cells, the large quantity can easily
be seen and looks like translucent strands of mucous-like cotton. In this lab, you will isolate your
own chromosomal DNA from a large quantity of cheek cells.
You will first collect a sample of intact cheek cells by swishing a small amount of sports
drink in your mouth. Sports drinks contain salt at a concentration compatible with the osmotic
environment of the cell. The sports drink prevents the cells from breaking open and releasing
their DNA before they are collected.
You will then lyse (break) the phospholipids membranes of your collected cheek cells
with a detergent based cell lysis solution. This solution dissolves the phosophlipids of cell
membranes by forming water-soluable complexes with them. Once the cell membranes are
degraded, the containments of the cell will flow out and create a collection of dissolves
membranes, cellular proteins, DNA, and other contents. The collection is called cell lysate and is
not visible to the naked eye.
However, DNA is insoluble in ethanol. Therefore, you will apply a layer of ethanol on
top of the cell lysate to visualize the DNA. Once the ethanol hits the cell lysate, DNA will
precipitate (ie: formation of a solid) out of solution, forming a translucent cloud of fine, stringy
fibers at the point where the ethanol and cell lysate meet. The salt in the sports drink allows the
strands to clump together as they precipitate. You will observe your very own DNA in the 15mL tube. Have fun!
Essential Questions:
What are the major components of DNA? How do they relate to the overall function of DNA?
How does the molecular structure and packaging of DNA allow for its function in heredity and
cell reproduction?
DNA Extraction Lab Page.
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Procedure:
1. Use a marker to write your initials on your 15-mL tube.
2. Get a 2-mL cup of the sports drink and swish the sports drink around in your mouth for 1 full
minute. As you swish, gently and continuously scrape the insides of your cheeks with your teeth
to help release the cheek cells.
3. After 1 minute of swishing, spit the sports drink with the collected cheek cells back into the
small plastic cup.
4. Carefully pour the contents of the small plastic cup into your labeled 15-mL tube. Place the
cap on your 15-mL tube. Discard the cup.
5. Bring your capped 15-mL tube to the Solution Station. Use the plastic pipet to add 2-mL of
cell lysis solution to your collected cheek cells.
6. Recap your 15-mL tube tightly and invert the tube five times. The inverting of the tube will
mix the cell lysis solution with the collected cheek cells. Let the 15-mL tube sit for 2 minutes.
7. After the 2 minutes, bring your capped 15-mL tube to the Solution Station. Hold the tube at an
angle and using a plastic pipet, carefully add cold 70% ethonal by running it down the inside of
the tube. Add the ethanol until the total volume of liquid reaches
12 -13 mL of total solution.
Two distinct layers should begin to appear. One layer is the cheek cell lysate layer and the other
is the ethanol layer. Do not mix the two layers.
8. Wispy strands of translucent DNA will begin to clump together where the ethanol layer meets
the cell lysate layer. The DNA will look like cobwebs extending up from the cheek cell lysate
layer. Small bubbles in the ethanol layer will also begin to appear.
9. Place your 15-mL tube upright in a beaker or test tube rack. Let the tube stand undisturbed for
a minimum of 10 minutes. During this time, the DNA will continue to come out of solution and
become visible. DNA yields from different samples will vary.
Materials:
 Marker
 15-mL plastic tube with cap
 2-mL cup of the sports drink
 2-mL of cell lysis solution
 10-11 mL of 70% ethonal
 Beaker
 Gloves and Goggles
DNA Extraction Lab Page.
Questions:
1. Describe the way long strands of double-helical DNA fits into the nucleus of a single cell?
2. Why is a sports drink used to collect the cheek cells instead of water?
3. What does the cell lysis solution do to the cells’ membrane?
4. Why can you see the extracted DNA with the naked eye?
5. How does the DNA in the cell lysate become visible?
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