Extracting DNA from
the DNA in strawberries like that in humans?
Materials (per student group)
extraction liquid (soapy, salty water)
apparatus: cheesecloth, funnel, small beaker
- If the
green leaves on the strawberry have not yet been removed, do so by pulling
the strawberry into the Ziploc bag and smush for about two minutes. You need to completely crush the strawberry. You do not want this mixture
to be really bubbly. The less
bubbles the better.
you’re finished smushing, put 10 ml of the DNA extraction liquid into the
for another minute. Be careful not
to make too many soap bubbles.
the scissors to cut a corner of the Ziploc to allow mixture to be poured
into the filter.
the liquid through the cheese cloth into the beaker. If it runs slowly, you may squeeze the
cheese cloth to get the liquid through.
pour the filtered strawberry liquid into your glass vial until it is
carefully pour the ethanol into the glass vial.
the tube several times to mix the liquids. (do not shake)
for the development of several large air bubbles that have a white cloudy
substance attached to them. The
cloudy substance is DNA!
- If you
would like, take a toothpick and spin and stir the DNA like you are making
cotton candy. If you tilt the
vile, you'll get more DNA
out the DNA. It will look like
mucus or egg white. As it dries,
it will look like a spider web.
The fibers are millions of DNA strands!
look at the DNA under a microscope, put the glob on a clean slide and
gently stretch it apart using two toothpicks. The fibers will be easier to see in the stretched apart
attention to the characteristics of the DNA as it precipitates.
Draw what your DNA looks like
under the microscope below:
Low power High
order to study our genes, scientists must extract the DNA from human
tissue. Would you expect the method
of DNA extraction we used for the strawberry to be the same for human
DNA? Why or why not?
- Is DNA
the same in any cell in the human body?
Explain your answer.
- If you
wanted to examine a suspect's DNA, which cells would you use and why?
list two reasons why an investigator might want to study the DNA of a