Download DNA Extraction - Sterlingmontessoriscience

How to get DNA from common food
items
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A routine procedure to collect DNA for
subsequent molecular or forensic
analysis.
DNA is extracted from human cells for a
variety of reasons. With a pure sample
of DNA you can test a newborn for a
genetic disease, analyze forensic
evidence, or study a gene involved in
cancer.
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Break the cells open to expose DNA
Remove membrane lipids by adding
detergent
Precipitate DNA with an alcohol —
usually ethanol or isopropanol. Since
DNA is insoluble in these alcohols, it
will aggregate together, giving a pellet
upon centrifugation. This step also
removes alcohol-soluble salt.
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University of Utah
◦ Genetic Science Learning Center:
http://learn.genetics.utah.edu/content/labs/
extraction/
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Strawberries
Bananas
Green Peas
Wheat Germ
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½ cup of DNA (peas, strawberries,
bananas)
Large pinch of table salt
(less than 1/8 teaspoon)
Twice as much cold
water as DNA source
(about 1 cup)
Blend on high for
15 seconds
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Some protocols require heating at a low
(50’C) temperature to ensure that all of
the cell wall material is broken down.
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Filter or strain out the extra material
and the “naturant” solution containing
DNA can be used for the extraction.
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Add about 2
tablespoons of
detergent, swirl to
mix.
Let the mixture sit
for 5-10 minutes.
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Blending separated
the cells, but each
cell is surrounded by
a sack (the cell
membrane). DNA is
found inside a second
sack (the nucleus)
within each cell.
To see the DNA, we
have to break open
these two sacks
using detergent.
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A cell's membranes have two layers of
lipid (fat) molecules with proteins going
through them.
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When detergent comes close to the cell,
it captures the lipids and proteins.
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Pour the mixture
into test tubes or
other small glass
containers, each
about 1/3 full.
Add a pinch of
enzymes to each
test tube and stir
gently.
Be careful! If you stir too hard, you'll break up
the DNA, making it harder to see.
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Enzymes are proteins that
help chemical reactions
happen more quickly. Without
enzymes, our bodies would
grind to a halt.
In this experiment, the enzyme
we use comes from meat
tenderizer and cuts proteins
just like a pair of scissors.
You can also use fresh
pineapple juice or contact lens
cleaning solution as an
enzyme.
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The DNA in the nucleus of the cell is
molded, folded, and protected by
proteins. The meat tenderizer cuts the
proteins away from the DNA.
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Tilt your test tube and
slowly pour rubbing
alcohol) into the tube
Pour it down the side so
that it forms a layer on
top of the fruit mixture.
Pour until you have
about the same amount
of alcohol in the tube as
fruit mixture.
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DNA will rise into
the alcohol layer
from the fruit
layer
Use a wooden
stick draw DNA
into the alcohol
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Alcohol is less dense
than water, so it floats
on top.
Since two separate
layers are formed, all
of the grease and the
protein that we broke
up in the first two
steps and the DNA
have to decide which
layer to go to.
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In this case, the protein and
grease parts find the bottom,
watery layer the most
comfortable place, while the
DNA prefers the top, alcohol
layer.
DNA is a long, stringy
molecule that likes to
clump together.
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Compare it with
DNA extracted
from other
sources.
You may want to
save it inside of a
vial of alcohol.
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The vial containing DNA may be made
into a wearable necklace: