AP Biology
Name:
Period:
Date:
Gel Electrophoresis Lab Results
1. Measure the distance that each band traveled in millimeters. For each sample measure
from the bottom of the sample well to the bottom of each DNA fragment.
2. Record the measurements for the DNA Marker Standard, Crime Scene, and suspects in
the corresponding lanes below to scale.
ANALYSIS
DNA Marker
Crime Scene
Suspect #1
Suspect #2
3. Based on your DNA electrophoresis analysis which suspect’s DNA was at the crime scene?
1
Table 1 DNA Marker Standard (Hind III)
Fragment
1 (Top)
2
3
4
5
6
7
8
Table 3
Fragment
1 (Top)
2
3
4
5
6
7
8
Distance Migrated (mm)
Not Imaged
Table 2
Length (bp)
23,109
9,416
6,557
4,361
2,328
2,027
564
125
Suspect 1 DNA Sample
Distance Migrated (mm)
Fragment
1 (Top)
2
3
4
5
6
7
8
9
10
Table 4
Length (bp)
2
Fragment
1 (Top)
2
3
4
5
6
7
8
9
10
Crime Scene DNA Sample
Distance Migrated (mm)
Length (bp)
Suspect 2 DNA Sample
Distance Migrated (mm)
Length (bp)
3
Concept Questions:
1. Different bacteria contain different restriction enzymes. What is their function?
2. How would using an agarose gel higher than 8% change the results?
3. What would occur if the sample wells containing the DNA were placed closest to the
red electrode instead of the black?
4. Both electrophoresis and paper chromatography are used for separating molecules.
What are two similarities and two differences between these two methods?
5. Describe the purpose of each component involved in gel electrophoresis.
Agarose gel-
TBE buffer-
Polarity of the electrophoresis chamber-
Voltage-
DNA samples (restriction fragments)-
DNA stain-
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6. The restriction endonuclease (restriction enzyme), EcoR1 recognizes the nucleotide
sequence GAATTC (recognition site), and Hind III recognizes AAGCTT. If you add
EcoR1 to a linear DNA sample, Hind III to a second sample, and both to a third, run a gel
separation, the following occurs.
Hind III
_____
Eco R1
Double
_____
_____
_____
_____
_____
_____
A student viewing the gel, draws the following map of the linear DNA:
GAATTC cut site
a). How did the student know to show the EcoR1 restriction enzyme cut site as identified
above?
AAGCTT cut site
GAATTC cut site
b) Why would the sample with both restriction enzymes be identified as shown above?
7. What are the odds that either recognition sequence from question #6 will appear in any
random DNA? (This is a probability question. Give a numeric answer.)
8. After running a gel you are left with the following three fragments: 22kb, 18kb, 4kb.
Mark the restriction sites and label the fragments on the plasmid below. What would the
fragment banding on the gel look like?
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