Transcript 3 Gel Electrophoresis

DNA Fingerprinting and Gel
Electrophoresis Notes
June 2, 2016
DNA fingerprints
• Made by cutting DNA in very specific places.
• How do we cut DNA?
Do you remember
• Restriction Enzymes
what a restriction
enzyme is?
I. DNA Fingerprinting
A. DNA is cut using ____________________.
1. Because no two individuals have identical
DNA, no two individuals will have the same
length fragments
B. Once the restriction enzyme has successful cut
the DNA into fragments, the next step in
analyzing the DNA is to use a gel
electrophoresis
II. Gel Electrophoresis
A. Gel electrophoresis is a technique used to
separate the DNA fragments according to their
size
B. DNA fragments are placed in wells on a sheet
of agarose gel
1. Gel is slightly porous and allows fragments to
move through the gel at a rate relative to their
size
C. An electric current is applied to the sheet
D. DNA is negatively charged and will move in an
electric field toward the positive pole
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Which size fragments do you expect to move
faster through the gel?
1. Smaller fragments move through the gel at a
faster rate compared to the larger pieces
E. Bands will be produced on the gelatin where the
fragments accumulate
1. The more fragments that accumulate in one spot,
the thicker the line will be in the gel
F. DNA bands must be stained to make them visible
III. Uses for DNA Fingerprinting and Gel
Electrophoresis
A. Used in forensics as a way
to match a sample from a
crime scene to a suspect’s
DNA
B. Used in paternity cases
where the father is
unknown
1. Each fragment in the
child’s DNA must match
at least one of the
parent’s fragments
2.
http://www.sumanasinc.com/webcontent/a
nimations/content/paternitytesting.html
C. Used to analyze genes to test for presence of
different alleles
1. If a person was homozygous for a trait, the DNA
would be cut by the same restriction enzyme in
the same place because alleles are the same
a. Fragments would be at the same point when run
through a gel electrophoresis
Allele from Mom
Allele from Dad
2. If a person was heterozygous for a trait, the DNA
would be cut by the same restriction enzyme in
different places because the alleles are different
a. Fragments would not be at the same point in the
gel electrophoresis
Allele from Mom
Allele from Dad
USE THESE SLIDES UP ABOVE IF NOT
TEACHING THIS FIRST…
Recombinant DNA
• Recombinant DNA contains DNA
from 2 or more different sources.
• So how does DNA get from one species
to another?
• Vector: something used to transfer
DNA from one organism to another
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Microinjection
Gene Gun
Virus
Bacteria Plasmid
Transgenics
• Genetic engineering
makes it possible to
transfer DNA sequences
from one organism to
another
• REMEMBER- DNA is
universal
• A gene taken from one
species can be replicated
in another species.
• So how do I take a gene from one organism
and put it into another?
• We have to cut it using a Restriction
Enzyme