In this lesson we
• examine the use of DNA technology in forensics,
medicine, and agriculture (SB2f)
Terms and topics related to DNA Technology:
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Biotechnology
cloning
DNA fingerprinting
genetic engineering
Human Genome Project
plasmid
recombinant DNA
What is biotechnology?
• The use of living organisms to do
practical tasks.
• Early examples:
– The use of microorganisms to make
cheese and wine
– Selective breeding of livestock and crops
– Production of antibiotics from
microorganisms
– Production of monoclonal antibodies
Goal of biotechnology today:
• To find practical applications of DNA
tecniques for the improvement of
human health and food production
– Making gene products using Genetic Engineering
– Uses in basic research
– Medical uses. Diagnosis of disease
– Making vaccines and other pharmaceutical
products
– Forensic uses of DNA such as DNA fingerprinting
– Agricultural uses such as making transgenic
plants
DNA Technology
• What we can do with DNA and what it
can do for us
DNA TECHNOLOGY
DNA recombination or genetic
engineering is the direct
manipulation of genes for practical
purposes
Recombinant DNA technology
• Refers to the set of techniques for
combining genes from different sources
in vitro( in a test tube) and transfering this
DNA into a cell so it can be expressed.
• These techniques were first developed
around 1975 and resulted in the
appearance of the Biotechnology
industry
The tools of recombinant DNA
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Plasmids
Restriction enzymes
Gel electrophoresis
PCR ( polymerase chain reaction)
– Researchers can insert desired genes into
plasmids, creating recombinant DNA
•
And insert those plasmids into bacteria
Bacterium
Cell containing gene
of interest
1 Plasmid
isolated
2 DNA
isolated
3 Gene inserted
into plasmid
Plasmid
Bacterial
chromosome
Recombinant DNA
(plasmid)
DNA
Gene of
4 Plasmid put into interest
bacterial cell
Recombinant
bacterium
5 Cell multiplies with
gene of interest
Copies of gene
Gene for pest
resistance
inserted into
plants
Figure 12.1
Copies of protein
Clone of cells
Gene used to alter bacteria
for cleaning up toxic waste
Protein used to
make snow form
at higher
temperature
Protein used to dissolve blood
clots in heart attack therapy
Genetic Engineering
• DNA from one
species is inserted
into another
species.
• Ex. Human Insulin
for diabetics is
now made by
bacteria cells!
•Therapeutic hormones
– In 1982, humulin, human insulin produced
by bacteria
•
Became the first recombinant drug
approved by the Food and Drug
Administration
Figure 12.7A
Restriction enzymes cut DNA at
specific sequences in the DNA
Restriction enzymes = scissors
Recombinant DNA
Two pieces of DNA cut
with the same restriction
enzyme will be able to
re-combine with each
other.
Plants
• 1) Examples of transgenic plants with resistance
to viruses…
potatoes, tomatoes, tobacco
• 2) Examples of transgenic plants with resistance
to insects… corn, cotton
• 3) resistance to herbicides
• 4) slow down spoilage in tomatoes
• 5) Extreme example – strawberries that are
resistant to drought, salt, insects, viruses,
cold and frost, and improved taste
Animals
• Bacteria now produce all of the
following…
– Human growth hormone (HGH) –
– Human insulin (replaced cow and pig insulin for
human therapy )
– Follicle-stimulating hormone
– Factor VIII (replaced clotting factors taken from
human blood.)
Electrophoresis
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Separation of charged molecules
in an electric field.
Nucleic acids have 1 charged
phosphate (- charge) per
nucleotide. Separation based
(mostly) on length: longer
molecules move slower.
Done in agarose gel matrix to
stabilize.
average run: 100 Volts across a
10 cm gel, run for 2 hours.
Stain with ethidium bromide:
bonds between DNA bases and
fluoresces orange.
Run alongside standards of known
sizes to get lengths
Gel electrophoresis sorts DNA molecules
by size
Mixture of DNA
molecules of
different sizes
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Longer
molecules
Power
source
Gel
+
Shorter
molecules
+
Figure 12.10
Completed gel
– After digestion by restriction enzymes
•
The fragments are run through a gel
1
–
2
Longer
fragments
z
x
w
Shorter
fragments
Figure 12.11B
+
y
y
Crime
• Forensic science is the use of scientific
knowledge in legal situations.
• The DNA profile of each individual is highly
specific.
• The chances of two people having exactly
the same DNA profile is 30,000 million to 1
(except for identical twins).
•DNA and Crime Scene Investigations
– Many violent crimes go unsolved
•
For lack of enough evidence
– If biological fluids are left at a crime scene
•
DNA can be isolated from them
– DNA fingerprinting is a set of laboratory
procedures
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That determines with near certainty whether two
samples of DNA are from the same individual
That has provided a powerful tool for crime
scene investigators
Investigator at one
of the crime scenes
(above), Narborough,
England (left)
DNA Fingerprinting
1st-The DNA molecule is cut with restriction enzymes
2nd- we have to separate the fragments
This is done by a technique called gel electrophoresis
The DNA is placed on a tray filled with gel through
which an electric current runs causing the fragments
to move through the gel. The segments separate by
how far they move in the gel according to size.
The DNA will form bands corresponding to the bases
(and no two people have the same sequence of bases) in
the gel which are unique for each individual. This is
DNA fingerprinting
Example
• A violent murder occurred.
• The forensics team retrieved a blood
sample from the crime scene.
• They prepared DNA profiles of the blood
sample, the victim and a suspect as
follows:
Does suspect DNA bands match
DNA from the crime scene?
Suspects
Profile
Blood sample
from crime
scene
Victims
profile
– DNA fingerprinting can help solve crimes
Defendant’s
blood
Blood from
defendant’s clothes
Figure 12.12A
Victim’s
blood
Figure 12.12B
DNA Fingerprinting
Gel Electrophoresis
separates pieces of
DNA based on size
(after being cut up with
restriction enzymes)
Different people will
have different
banding patterns.
Related individuals will
have similar
patterns.
Solving Medical Problems
DNA profiles can be used to determine whether a
particular person is the parent of a child.
A childs paternity (father) and maternity(mother)
can be determined.
This information can be used in
• Paternity suits
• Inheritance cases
• Immigration cases
Example: A Paternity Test
• By comparing the DNA profile of a
mother and her child it is possible to
identify DNA fragments in the child
which are absent from the mother and
must therefore have been inherited
from the biological father.
Does this man’s DNA match the
DNA of the child?
Mother
Child
Man
Cloning organisms
• A body cell from one
organism and an egg cell
from another are fused
• The resulting cell divides
like a normal embryo
29
Cloning
• Clone- a member
of a group of
genetically
identical cells
• May be produced
by asexual
reproduction
(mitosis)
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What is cloning?
• Reproductive cloning
– Making an exact copy of a
pre-existing or currently
existing organism.
• Therapeutic cloning
– Embryos are grown and
stem cells from the embryo
are harvested to be used in
research to develop
treatment for cancer,
Alzheimer’s, etc.
– Very controversial b/c it
kills the embryo in the
process.
Human Genome Project
• Started 1988, finished 2001,
the entire sequence of bases
in human DNA is now known.
• This multi-national effort has
led to increased knowledge
of …
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Human genetic diseases
Gene therapies
Evolutionary relationships
Cellular functions
Cancer genes
Gene Libraries
• Human genes (and
other genes of
interest) can be stored
inside bacteria cells
and viruses which can
be saved and grown
for use in research.
•
This may also
preserve the genes of
endangered or extinct
species.
Review and Summarize
• -use of DNA technology in forensics, medicine,
and agriculture (SB2f)
Terms and topics related to DNA Technology:
–
–
–
–
–
–
–
biotechnology
Cloning
DNA fingerprinting
genetic engineering
Human Genome Project
plasmid
recombinant DNA