DNA Fingerprinting
Names ______________ ______________
______________
Sometime between the hours of 4:00 P.M. and 7:00 A.M., An individual attempted to organize and carry out a catastrophe
on the resident of the aquarium in A209. In their haste to make off with Stanley the Turtle and her eggs, the perpetrator
must have received a cut while attempting to capture the innocent creature. As a result, a small sample of blood
containing DNA was left behind. The DNA was duplicated and a map was produced. Your job is to make a DNA map of
one of ten suspects involved with this case, which may or may not match the DNA found at the crime scene.
Procedure:
Read ALL the instructions before beginning!
Read: Pg 279-280
Persons 1 and 2
MAKE ONE LINE OF DOUBLE STRANDED DNA:
1. Label each of the lines of DNA bases on the suspect page, so
you know what order they are in. (1,2,3…)
2. Cut each of the lines of DNA bases apart and tape them end
to end, making sure that the beginning of line 2 attaches to
the end of line 1, etc. You will end up with a single long
strand that represents a piece of a DNA molecule (as seen
below).
CUT THE DNA USING A “RESTRICTION ENZYME”:
3. Draw a line in front of and underneath the sequence GAATTC every time it appears on the strand of DNA.
Continue the line down just after the line below reads CTTAAG (the same as the sequence you just found, just
written backwards). Be careful as the sequence may start on one piece of paper and finish on the one taped at its
end. It should look something like the picture below
4. Next, use a “restriction enzyme” (scissors) that recognizes the nitrogen base
sequence GAATTC to cut the DNA strand into many smaller pieces (along the
lines you just drew). The result will be many “Z” shaped pieces of varying length similar to the shape above.
5. Place the first and last pieces of the strand that do not form a “Z” shape into the recycle bin. (Don’t use them!)
6. For each segment, count the number of bases on either the top OR the bottom line. Using the formula below
calculate the distance each segment will be moving from the starting point during the gel electrophoresis process.
Record AND CIRCLE this number on the front of each segment. (round to the nearest tenth)
500
# of bases
=
number of cm the segment will move away from the starting point
7. Once person #3 is done, tape or glue each segment at the correct location on the paper. If there are some
segments that have the same circled value – stack them together.
Person 3 MAKE THE “GEL”:
1. Get a large piece of paper and a meter stick. Draw a line the length of the paper the long way, about 3 cm from
the edge of the paper
2. Mark and label every cm on the line – choosing a zero point at the bottom and going until ~ 80 cm at the top.
3. Help the other members of the group.
RUN THE CUT-UP DNA THROUGH THE “GEL” TO SPREAD OUT THE SEGMENTS BY LENGTH:
 During the electrophoresis process of DNA mapping, the different size segments of DNA move through the gel at
different speeds – smaller pieces move faster and larger pieces move slower. Therefore at the end of the process the
smaller pieces have moved a longer distance than the larger pieces.
 To simulate the results of the electrophoresis process you must move each segment up the scale the distance (in cm)
you calculated (and circled on the front of each segment). Glue or tape the DNA segments in place.
 Use the line under the bases for measuring purposes.
 When all of the segments have been glued in place, you have your DNA map.
 Write a profile of your suspect. Include anything you feel is relevant – name, aliases, description, occupation,
hobbies, address, etc. Put this information on the front of your DNA map.
 When all the suspects’ maps have been completed, we will compare them to the DNA found at the crime scene.
Questions
1.
Make up a (fake) profile for your suspect and write it below:
Name:
Alias(s):
Physical description:
Distinguishing characteristics:
(scars, tattoos, etc)
Employment:
Hobbies:
Motive (why??):
2. Is your suspect the guilty party?
3. Explain the steps involved in the process of gel electrophoresis and what people are looking at
when comparing DNA fingerprints. (re-read pg 279-280 if necessary!)
3. Explain how and why DNA fingerprinting uses only part of the DNA molecule.
4. Sometimes there may not be very much DNA in a sample and it must be copied many times
before a DNA fingerprint can be made. Use your book to explain the process for making many
copies of a single piece of DNA. Present your answer as a list of steps, 1,2,3… (hint: PCR)