Download DNA Extraction Lab 2016

DNA Extraction Lab
Extraction means to take something out. Today we will extract the DNA
from a strawberry.
This is the same process forensic scientists would use to extract
DNA from evidence (e.g. blood samples) taken from a crime scene to find
the perpetrator, or what Miss. S. did as her job – getting DNA from ancient
samples (animal poop) to learn about the food eaten by sloths and other
prehistoric animals!
Every living thing contains DNA in its cells...you, your dog, the
flowers in your garden and the food you eat! Different species of plants
and animals have different numbers of chromosomes. A high number
does not mean the organism is “smarter” or bigger or better in any way.
For example, we know that humans have 23 pairs of chromosomes, for a
total of 46, but rattlesnakes have a total of 184 chromosomes! A
mosquito only has 6 chromosomes and wheat has 42. We will extract the
DNA from strawberries because they have a high number of
chromosomes - 56 in each cell.
We will smoosh up a strawberry and add a buffer (which will dissolve and
break up the cell parts, but keep the DNA intact). We will then filter the
mixture to separate the DNA from the rest of the cell parts. Then we will
add cold ethanol. DNA will not dissolve in cold ethanol, so we will be able
to remove it from the test tube using a popsicle stick to feel it. Remember,
DNA is a very long but thin molecule, we will be able to see/feel it
because we have millions of strands, from millions of strawberry cells.
Materials:
ziploc bag
1 strawberry
Graduated cylinder
10 mL DNA extraction buffer (water, soap, salt)
Filter paper
Funnel
Retort stand
Beaker
popsicle stick
20 mL cold ethanol
Micropipette
Buffer:
The extraction buffer is a solution of water, soap and salt. The soap helps
to dissolve the cell membrane. The salt breaks up protein and all of the
organelles from the strawberry cells.
In a beaker, add:
20 mL water
10 mL dish soap
1 small pinch of salt
Gently stir your mixture. Do not make it bubbly.
Filter Set-Up:
Fold the filter paper in half and in half again to make a triangle. Place
your folded filter paper into the funnel and the funnel in the ring of the
retort stand.
Procedure:
1. Put one strawberry in your bag.
2. Smoosh up the strawberry for 2 minutes. Do NOT break the bag!
3. Add 10mL of buffer to the bag – use the micropipette with a clean tip
4. Mush the strawberry in the bag again for 1 minute.
5. Pour the strawberry mush into the filter and funnel. Let it drip into
your beaker.
6. Slowly pour 20 mL of cold ethanol into the tube.
7. Dip the popsicle stick into the test tube and slowly pull it out.
Observe what is on the end of the stick.
Questions:
1. What was the job of the soap in the buffer?
2. What was the job of the salt in the buffer?
3. What was the job of the cold ethanol?
5. Why is it important for scientists to be able to remove DNA from
an organism? List two reasons.
6. A) Is there DNA in your food?
B) How do you know?