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Chapter 12
DNA Technology
PowerPoint® Lectures for
Campbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition
– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Lectures by Edward J. Zalisko
© 2013 Pearson Education, Inc.
Biology and Society:
DNA, Guilt, and Innocence
• DNA profiling is the analysis of DNA samples that
can be used to determine whether the samples
come from the same individual.
• DNA profiling can therefore be used in courts to
indicate if someone is guilty of a crime.
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Biology and Society:
DNA, Guilt, and Innocence
• DNA technology has led to other advances in the
– creation of genetically modified crops and
– identification and treatment of genetic diseases.
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RECOMBINANT DNA TECHNOLOGY
• Biotechnology
– is the manipulation of organisms or their
components to make useful products and
– has been used for thousands of years to
– make bread using yeast and
– selectively breed livestock for desired traits.
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RECOMBINANT DNA TECHNOLOGY
• Biotechnology today means the use of DNA
technology, techniques for
– studying and manipulating genetic material,
– modifying specific genes, and
– moving genes between organisms.
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RECOMBINANT DNA TECHNOLOGY
• Recombinant DNA is constructed when scientists
combine pieces of DNA from two different sources
to form a single DNA molecule.
• Recombinant DNA technology is widely used in
genetic engineering, the direct manipulation of
genes for practical purposes.
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Figure 12.1
Applications: From Humulin to Foods to “Pharm”
Animals
• By transferring the gene for a desired protein into a
bacterium or yeast, proteins that are naturally
present in only small amounts can be produced in
large quantities.
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Making Humulin
• In 1982, the world’s first genetically engineered
pharmaceutical product was sold.
• Humulin, human insulin
– was produced by genetically modified bacteria and
– is used today by more than 4 million people with
diabetes.
• Today, humulin is continuously produced in
gigantic fermentation vats filled with a liquid culture
of bacteria.
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Making Humulin
• DNA technology is used to produce medically
valuable molecules, including
– human growth hormone (HGH),
– the hormone erythropoietin (EPO), which
stimulates production of red blood cells, and
– vaccines, harmless variants or derivatives of a
pathogen used to prevent infectious diseases.
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Genetically Modified (GM) Foods
• Today, DNA technology is quickly replacing
traditional breeding programs.
• Scientists have produced many types of
genetically modified (GM) organisms, organisms
that have acquired one or more genes by artificial
means.
• A transgenic organism contains a gene from
another organism, typically of another species.
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Genetically Modified (GM) Foods
• In the United States today, roughly half of the corn
crop and more than three-quarters of the soybean
and cotton crops are genetically modified.
• Corn has been genetically modified to resist insect
infestation, attack by an insect called the European
corn borer.
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Figure 12.4
Genetically Modified (GM) Foods
• Strawberry plants produce bacterial proteins that
act as a natural antifreeze, protecting the plants
from cold weather.
• Potatoes and rice have been modified to produce
harmless proteins derived from the cholera
bacterium and may one day serve as edible
vaccines.
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“Pharm” Animals
• A transgenic pig has been produced that carries a
gene for human hemoglobin, which can be
– isolated and
– used in human blood transfusions.
• In 2006, genetically modified pigs carried
roundworm genes that produce proteins that
convert less healthy fatty acids to omega-3 fatty
acids.
• However, unlike transgenic plants, no transgenic
animals are yet sold as food.
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Recombinant DNA Techniques
• Bacteria are the workhorses of modern
biotechnology.
• To work with genes in the laboratory, biologists
often use bacterial plasmids, small, circular DNA
molecules that replicate separately from the larger
bacterial chromosome.
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Figure 12.7
Bacterial
chromosome
Remnant of
bacterium
Colorized TEM
Plasmids
Recombinant DNA Techniques
• Plasmids
– can carry virtually any gene,
– can act as vectors, DNA carriers that move genes
from one cell to another, and
– are ideal for gene cloning, the production of
multiple identical copies of a gene-carrying piece of
DNA.
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Recombinant DNA Techniques
• Recombinant DNA techniques can help biologists
produce large quantities of a desired protein.
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Figure 12.8
Bacterial cell
1
2 Isolate DNA.
Isolate plasmids.
Cell containing
the gene of interest
3
Plasmid
Cut both DNAs
with same
enzyme.
Gene
Other
of
interest genes
4
DNA fragments
from cell
DNA
Mix the DNA fragments and join them together.
Gene of interest
Recombinant DNA plasmids
5 Bacteria take up recombinant plasmids.
Recombinant bacteria
Bacterial clone
6 Clone the bacteria.
7 Find the clone with the gene of interest.
A gene for pest
resistance is
inserted into
plants.
Some uses
of proteins
Some uses
of genes
A gene is used to alter
bacteria for cleaning
up toxic waste.
8
Genes may
be inserted
into other
organisms.
The gene
and protein
of interest
are isolated
from the
bacteria.
Bacteria
produce
proteins,
which can be harvested
and used directly.
A protein is used to
dissolve blood clots
in heart attack
therapy.
A protein is used to prepare
“stone-washed” blue jeans.
Figure 12.8c
Some uses
of genes
Genes for
cleaning up
toxic waste
Genes may
be inserted
into other
organisms.
Gene
for pest
resistance
Some uses
of proteins
8 The gene
and protein
of interest
are isolated
from the
bacteria.
Harvested
proteins
may be
used
directly.
Protein for
dissolving
clots
Protein for
“stone-washing”
jeans
A Closer Look: Cutting and Pasting DNA with
Restriction Enzymes
• Recombinant DNA is produced by combining two
ingredients:
1. a bacterial plasmid and
2. the gene of interest.
• To combine these ingredients, a piece of DNA
must be spliced into a plasmid.
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A Closer Look: Cutting and Pasting DNA with
Restriction Enzymes
• This splicing process can be accomplished by
– using restriction enzymes, which cut DNA at
specific nucleotide sequences (restriction sites),
and
– producing pieces of DNA called restriction
fragments with “sticky ends” important for joining
DNA from different sources.
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Figure 12.9-4
Recognition site (recognition sequence)
for a restriction enzyme
1 A restriction enzyme cuts the
DNA into fragments.
2
DNA
Restriction
enzyme
A DNA fragment is added from
another source.
3 Fragments stick together by
base pairing.
4
DNA ligase joins the fragments
into strands.
DNA
ligase
Recombinant DNA molecule
A Closer Look: Obtaining the Gene of Interest
• Another approach is to
– use an automated DNA-synthesizing machine and
– synthesize a gene of interest from scratch.
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DNA PROFILING AND FORENSIC SCIENCE
• DNA profiling
– can be used to determine if two samples of genetic
material are from a particular individual and
– has rapidly revolutionized the field of forensics,
the scientific analysis of evidence from crime
scenes.
• To produce a DNA profile, scientists compare
sequences in the genome that vary from person to
person.
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Figure 12.13-3
1 DNA isolated
2 DNA amplified
3 DNA compared
Crime scene Suspect 1 Suspect 2
Investigating Murder, Paternity, and Ancient DNA
• DNA profiling can be used to
– test the guilt of suspected criminals,
– identify tissue samples of victims,
– resolve paternity cases,
– identify contraband animal products, and
– trace the evolutionary history of organisms.
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DNA Profiling Techniques
The Polymerase Chain Reaction (PCR)
• The polymerase chain reaction (PCR)
– is a technique to copy quickly and precisely a
specific segment of DNA and
– can generate enough DNA, from even minute
amounts of blood or other tissue, to allow DNA
profiling.
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Figure 12.15
Initial
DNA
segment
1
2
4
8
Number of DNA molecules
Gel Electrophoresis
• DNA analysis
– compares the lengths of DNA fragments and
– uses gel electrophoresis, a method for sorting
macromolecules—usually proteins or nucleic
acids—primarily by their
– electrical charge and
– size.
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Figure 12.17-3
Mixture of DNA
fragments of
different sizes
Band of longest
(slowest) fragments
Power
source
Band of shortest
(fastest) fragments
Gel Electrophoresis
• The DNA fragments are visualized as “bands” on
the gel.
• The differences in the locations of the bands reflect
the different lengths of the DNA fragments.
© 2013 Pearson Education, Inc.
Figure 12.18
Amplified
crime scene
DNA
Amplified
suspect’s
DNA
Longer
fragments
Shorter
fragments
GENOMICS
• Genomics is the study of complete sets of genes
(genomes).
– The first targets of genomics research were
bacteria.
– As of 2011,
– the genomes of more than 1,700 species have
been published and
– more than 8,000 are in progress.
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Table 12.1
Table 12.1a
Table 12.1b
The Human Genome Project
• Begun in 1990, the Human Genome Project was a
massive scientific endeavor to
– determine the nucleotide sequence of all the DNA in
the human genome and
– identify the location and sequence of every gene.
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The Human Genome Project
• At the completion of the project,
– more than 99% of the genome had been
determined to 99.999% accuracy,
– about 3 billion nucleotide pairs were identified,
– about 21,000 genes were found, and
– about 98% of the human DNA was identified as
noncoding.
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The Human Genome Project
• The Human Genome Project can help map the
genes for specific diseases such as
– Alzheimer’s disease and
– Parkinson’s disease.
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Tracking the Anthrax Killer
• In October 2001,
– a Florida man died after inhaling anthrax and
– by the end of the year, four other people had also
died from anthrax.
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Tracking the Anthrax Killer
• In 2008, investigators
– completed a whole-genome analysis of the spores
used in the attack,
– found four unique mutations, and
– traced the mutations to a single flask at an Army
facility.
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Figure 12.21
Envelope
containing
anthrax spores
Colorized SEM
Anthrax
spore
Tracking the Anthrax Killer
• Although never charged, an army research scientist
suspected in the case committed suicide in 2008,
and the case remains officially unsolved.
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Tracking the Anthrax Killer
• The anthrax investigation is just one example of
the new field of bioinformatics, the application of
computational tools to molecular biology.
Additional examples include
– evidence that a Florida dentist transmitted HIV to
several patients,
– tracing the West Nile virus outbreak in 1999 to a
single natural strain of virus infecting birds and
people, and
– determining that our closest living relative, the
chimpanzee (Pan troglodytes), shares 96% of our
genome.
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HUMAN GENE THERAPY
• Human gene therapy
– is a recombinant DNA procedure,
– seeks to treat disease by altering the genes of the
afflicted person, and
– often replaces or supplements the mutant version
of a gene with a properly functioning one.
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Figure 12.24
Normal
human gene
1 An RNA version of a normal human
gene is inserted into a harmless
RNA virus.
RNA genome of virus
Inserted human RNA
Healthy person
2
Bone marrow cells of the patient
are infected with the virus.
3 Viral DNA carrying the human gene
inserts into the cell’s chromosome.
Bone marrow cell from the patient
Bone
marrow
4 The engineered
cells are injected
into the patient.
Bone of person
with disease
HUMAN GENE THERAPY
• Severe combined immunodeficiency (SCID) is
– a fatal inherited disease and
– caused by a single defective gene that prevents
the development of the immune system.
• SCID patients quickly die unless treated with
– a bone marrow transplant or
– gene therapy.
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HUMAN GENE THERAPY
• From 2000 to 2011, gene therapy has cured 22
children with inborn SCID.
• However, there have been some serious side
effects. Four of the children developed leukemia,
which proved fatal to one.
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SAFETY AND ETHICAL ISSUES
• As soon as scientists realized the power of DNA
technology, they began to worry about potential
dangers such as the
– creation of hazardous new pathogens and
– transfer of cancer genes into infectious bacteria
and viruses.
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SAFETY AND ETHICAL ISSUES
• Strict laboratory safety procedures have been
designed to
– protect researchers from infection by engineered
microbes and
– prevent microbes from accidentally leaving the
laboratory.
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The Controversy over Genetically Modified Foods
• GM strains account for a significant percentage of
several staple crops in the United States.
• Advocates of a cautious approach are concerned
that
– crops carrying genes from other species might
harm the environment,
– GM foods could be hazardous to human health,
and/or
– transgenic plants might pass their genes to close
relatives in nearby wild areas.
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Figure 12.26
The Controversy over Genetically Modified Foods
• In the United States, all projects are evaluated for
potential risks by a number of regulatory agencies,
including the
– Food and Drug Administration,
– Environmental Protection Agency,
– National Institutes of Health, and
– Department of Agriculture.
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Ethical Questions Raised by DNA Technology
• DNA technology raises legal and ethical
questions—few of which have clear answers.
– Should genetically engineered human growth
hormone be used to stimulate growth in HGHdeficient children?
– Should we try to eliminate genetic defects in our
children and their descendants?
– Should people use mail-in kits that can tell healthy
people their relative risk of developing various
diseases?
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Figure 12.27
Ethical Questions Raised by DNA Technology
• DNA technologies raise many complex issues that
have no easy answers.
• We as a society and as individuals must become
educated about DNA technologies to address the
ethical questions raised by their use.
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Evolution Connection:
The Y Chromosome as a Window on History
• Barring mutations, the human Y chromosome
passes essentially intact from father to son.
• By comparing Y DNA, researchers can learn about
the ancestry of human males.
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Evolution Connection:
The Y Chromosome as a Window on History
• DNA profiling of the Y chromosome has revealed
that
– nearly 16 million men currently living may be
descended from Genghis Khan,
– nearly 10% of Irish men were descendants of Niall
of the Nine Hostages, a warlord who lived during
the 1400s, and
– the Lemba people of southern Africa are
descended from ancient Jews.
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