The crime lab collected evidence from the scene of the crime – specifically, hair and blood samples. Now it is time for you to analyze the data and figure out “who done it”. You will do this by creating a DNA fingerprint with the samples that were collected.
As you learned in the mini-lecture, a DNA fingerprint is collected using the following methods
· Cut the DNA into pieces using restriction enzymes
· Copy the DNA many times to get more of it to work with
· “Run” the DNA through a gel to separate the different pieces (gel electrophoresis), which will separate the pieces of cut DNA by size
You are going to do this for the various samples you collected from the crime scene, and use that data to solve the crime.
Step 1. Cut the DNA into pieces using restriction enzymes. You use the restriction enzyme HaeIII to cut the DNA into pieces. HaeIII cuts the following way:
AAGGCCTAG gets cut into AAGG CCTAG
TTCCGGATC TTCC GGATC
So, every time the enzyme encounters the sequence “GGCC”, the DNA strand it cut between the G’s and C’s.
The DNA samples we are working with contain 2 short tandem repeat (STR) segments. The first repeat is CCACGT, and the second is CGC. Cut the DNA with the restriction enzyme, HaeIII. The first DNA sample (victim) is cut for you. Determine how many base pairs (bp) long each piece of DNA is once it has been cut.
(a) Victim:
CCGAGAGGCCCCACGTCCACGTGGCCCGCCGCCGCCGCCGCCGCCGCGGCCA
GGCTCTCCGGGGTGCAGGTGCACCGGGCGGCGGCGGCGGCGGCGGCGCCGGT
Answer:
Site 1: (16bp long) Site 2: (25bp long)
CCGAGAGG CCCCACGTCCACGTGG CCCGCCGCCGCCGCCGCCGCCGCGG CCA
GGCTCTCC GGGGTGCAGGTGCACC GGGCGGCGGCGGCGGCGGCGGCGCC GGT
The enzyme cut each time the target sequence appeared in our DNA sample. We counted the length (in base pairs) of the DNA pieces between the cuts. Cut the remaining DNA samples yourself, and determine how many base pairs each is.
(b) Suspect #1:
CCAGGCCCCACGTCCACGTCCACGTGGCCCGCCGCCGCGGCCTAAAGAGGCTA
GGTCCGGGGTGCAGGTGCAGGTGCACCGGGCGGCGGCGCCGGATTTCTCCGAT
Answer: Site 1 Site #2
c) Suspect #2
CCAGGCCCCACGTGGCCCGCCGCCGCCGCCGCCGCCGCCGCCGCGGCCTAAA
GGTCCGGGGTGCACCGGGCGGCGGCGGCGGCGGCGGCGGCGGCGCCGGATTT
Answer: Site 1 Site #2
d) Evidence (hair sample)
CCAGGCCCCACGTGGCCCGCCGCCGCCGCCGCCGCCGCCGCCGCGGCCTAAA
GGTCCGGGGTGCACCGGGCGGCGGCGGCGGCGGCGGCGGCGGCGCCGGATTT
Answer: Site 1 Site #2
e) Evidence (blood sample)
CCGAGAGGCCCCACGTCCACGTGGCCCGCCGCCGCCGCCGCCGCCGCGGCCA
GGCTCTCCGGGGTGCAGGTGCACCGGGCGGCGGCGGCGGCGGCGGCGCCGGT
Answer: Site 1 Site #2
Step 2. You use a machine to make many copies of your DNA pieces.
(assignment continues below)
Step 3. Gel Electrophoresis. You place you cut DNA samples into a gel electrophoresis machine. You have already determined how big each of your DNA pieces is (above). Use that information to draw what the gel would look from these samples. Each sample (victim, hair, etc) will have 2 bands on the gel – once for each of the cut pieces of DNA. Draw those on the gel below. The first (victim) is done for you.
Tech Tip: To draw on the gel, click on one of existing purple lines for the victim, copy, then paste. Move the line to the appropriate space on the gel. You may not be able to get the line exactly where you want it – but close counts in this assignment!
(
Victim
) (
Blood
) (
Hair
) (
S #2
) (
S #1
) Gel
(
50
bp
)
(
40
bp
)
(
15
bp
) (
5
bp
) (
10
bp
) (
20
bp
) (
30
bp
)(assignment continues below)
Step 4. Analysis. Based on the DNA evidence above, answer the following questions.
a) What conclusions can you make about the DNA collected from the hair sample left at the scene of the crime? How do you know?
b) What conclusions can you make about the DNA collected from the blood sample left at the scene of the crime? How do you know?
c) Who do you think committed the crime? What evidence is there to support this?
Mo_Q8
murder_mystery_assignment_fa13_rev.docx
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