Download DNA Extraction from Strawberries

DNA Extraction
from Strawberries
Post Lab
Protocol: Step by Step
• What was the purpose
of Mashing the
Berries?
– physically break apart
the tissues and cell
walls
Protocol: Step by Step
• Why did we filter the
strawberries through the
Cheesecloth?
– Remove
• seeds
• cell debris(cell walls,
membranes, organelles &
proteins.
– Filtrate (solution that passes
through the cheesecloth)
• contains organelles,
including nuclei and
mitochondria which house
DNA.
Protocol: Step by Step
• What was the purpose
of the Extraction
Buffer?
– Liquid soap
• dissolves the phosholipid bilayers of
the cell membrane and organelles
– Salt
• keeps the proteins in the extract layer
so they aren’t precipitated with the
DNA
Protocol: Step by Step
• Why were we
careful not to disturb
the
strawberry/alcohol
layer?
– DNA is less dense
than other material in
the cell mixture and
will accumulate
towards the top of
the cell mixture
Protocol: Step by Step
• What was the purpose of the cold
Isopropyl alcohol?
– Change the environment of the
DNA, causing the DNA to
precipitate away from other cellular
material.
– DNA : not soluble in alcohol
• When molecules are soluble, they are
dispersed in the solution and are
therefore not visible.
• When molecules are insoluble, they
clump together and become visible.
– The colder the alcohol, the less soluble
the DNA will be in it. This is why it is
important to keep it in the freezer or in
an ice bath.
Post Lab Questions
Question: Think about what
the DNA looked like….
Relate its chemical
structure to how it looks
when lots of it is clumped
together.
Post Lab Questions-key
Question: Think about what
the DNA looked like….
Relate its chemical
structure to how it looks
when lots of it is clumped
together.
– Answer: The DNA
precipitate look like long
and thin fibers. This makes
sense since the molecular
structure is so long and
narrow.
Post Lab Questions
• Question: DNA is soluble
in water, but not in isopropyl
alcohol. What does this fact
have to do with our method
of extraction? Explain what
happened when the isopropyl
alcohol came in contact with
the strawberry extract.
Post Lab Questions-key
• Question: DNA is soluble
in water, but not in isopropyl
alcohol. What does this fact
have to do with our method
of extraction? Explain what
happened when the isopropyl
alcohol came in contact with
the strawberry extract.
– Answer: The DNA was
soluble in the DNA extraction
buffer so we could not see it.
When it got stirred into the
alcohol, it clumped together
and formed thicker and thicker
strands large enough to see.
Post Lab Questions
• Question: A person
cannot see a single cotton
thread 100 feet away, but
if you wound thousands of
threads together into a
rope, it would be visible at
some distance. How is this
statement an analogy to
our DNA extraction?
Post Lab Questions-key
• Question: A person
cannot see a single cotton
thread 100 feet away, but
if you wound thousands of
threads together into a
rope, it would be visible at
some distance. How is this
statement an analogy to
our DNA extraction?
– Answer: DNA is far too
narrow to see, but if there
are many thousands of
strands together, it is thick
enough to be visible
Post Lab Questions
• Question: If you wanted
to extract DNA from a
living person, what cells
would you use and why?
Post Lab Questions-key
• Question: If you wanted
to extract DNA from a
living person, what cells
would you use and why?
– Answer: Blood is the
easiest tissue to obtain from
living humans. White blood
cells contain a nucleus,
while red blood cells do
not.
– Skin cells would also work
if only a small amount of
DNA were needed.
Post Lab Questions
•
Question: List two reasons why a scientist might
want to study the DNA of strawberries.
Post Lab Questions-key
•
Question: List two reasons why a scientist might
want to study the DNA of strawberries.
–
Answer:
1. To compare the DNA of a type of
strawberry that is more disease or frost
resistant than other strawberries
2. To study the evolutionary relatedness of
strawberries to other berries.
3. To study a gene that codes for a particular
protein in strawberries. For example,
strawberries are known to have some
chemical in them that slows the growth of
some tumors.
4. To clone a particular gene in
strawberries. Perhaps they want to make
large quantities of the protein that makes
strawberries red or produces the desired
flavor of strawberries