Download lecture 12, part 2, dna technology, 050509c

DNA Technology
http://www.livefromthepit.com
Lecture 12, Part 2
DNA is over 99.9 percent
identical for any two people
of the same sex.
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Much of the text material in the lecture notes is from our textbook,
“Essential Biology with Physiology” by Neil A. Campbell, Jane B.
Reece, and Eric J. Simon (2004 and 2008). I don’t claim authorship.
Other sources were sometimes used, and are noted.
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Outline
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Recombinant DNA
Human insulin
Genetically modified foods
DNA fingerprinting
Genomics
Gene therapy
Safety and ethical issues
Words and terms to know
Possible test items
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Recombinant DNA
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In the 1940s, researchers demonstrated that the genes from individual
bacteria could be combined in the laboratory without resorting to normal
reproduction.
Research over a span of 30 years, primarily using E. coli bacteria, led to
the development of recombinant DNA technology.
Genes from different sources are combined into the DNA molecule in a
host cell.
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Definitions
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A genetically-modified organism (GMO) is one that carries recombinant
DNA.
A transgenic organism is a GMO that carries DNA from different species.
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http://www.cbs.dtu.dk
Transgenic Organism
Glow-in-the-dark tobacco plant—contains genes from
a bioluminescent organism.
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Human Insulin
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Insulin is a protein produced by the pancreas to regulate the level of
glucose in the blood.
Diabetes (diabetes mellitus) results if insufficient insulin is produced.
A number of unhealthful outcomes can result from untreated diabetes.
http://www.dva.gov.au
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Bovine and Porcine Insulin
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Beginning in the 1920s, diabetes was treated using insulin from cows
and pigs.
Allergic reactions sometimes result since the protein structures are not
exactly alike.
By the 1970s, the supply of bovine and porcine insulin could not keep
up with the demand.
Ala
Thr
Human insulin (to the left) and
porcine insulin—the difference
in the protein structure is just
one amino acid: alanine versus
threonine.
http://www.bio.davidson.edu
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Synthetic Insulin
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Recombinant DNA technology enabled the mass production of synthetic
insulin.
Because the amino acid sequence for human insulin was already known,
researchers could identify the DNA nucleotide sequence that would code
for the protein.
Individual segments of DNA were synthesized and linked to form insulin
genes.
The artificially-produced human genes were inserted into E. coli bacteria
that could rapidly multiply and produce large quantities of insulin protein.
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Reliance on Synthetic Insulin
http://www.diabeticmommy.com
Today, more than four million people in the United
States rely on synthetic insulin.
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Genetically-Modified Foods
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Since antiquity, agricultural crops have been selectively bred to enhance
their use.
DNA technology is replacing traditional breeding programs to improve farm
productivity.
Some corn varieties, for example, have been genetically modified to resist
the European corn borer.
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Cornfield
http://www.precisiongps.com
Corn is a major economic crop, with a variety of uses
including for food products, high fructose corn syrup,
animal feed, and ethanol.
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European Corn Borer
http://ipm.uiuc.edu
The insect was first found in the
northeastern United States in 1917.
It has spread to the South, Midwest,
and High Plains regions.
http://ipm.uiuc.edu
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Strawberries and Rice
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Some strawberry varieties have been genetically modified to resist cold
weather.
Transgenic rice varieties have been developed as a source of iron and
beta carotene for vitamin A production.
http://www.agbioforum.org
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Transgenic ‘golden rice’ to
the right
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DNA Fingerprinting
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DNA technology has revolutionized forensics, the scientific analysis of
evidence in crime scene and other legal investigations.
The DNA sequence of every person is unique except in monozygotic
(identical) twins.
DNA fingerprinting can determine if genetic material is from the same
person or different people.
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Applications
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DNA fingerprinting has become a standard method for law enforcement
and legal proceedings since its introduction in 1986.
DNA can be obtained from body sources including blood, tissues, hair,
bone, saliva, and semen.
The technique has been used in a number of high-profile legal and civil
cases.
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More Recent Applications
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DNA technology continues to be used in identifying small fragments of
human remains from the terror attacks of September 11, 2001.
DNA has been used to exonerate prisoners who were innocent of the
charged crimes.
From the website of an appeals
attorney specializing in DNA
evidence.
http://dna.view.com
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DNA Fingerprinting Process
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The analysis of DNA ‘fingerprints’ has several major steps:
DNA collection, including maintaining the chain of custody
2. Amplifying (copying) the DNA to provide a sufficient sample
3. Cutting the DNA into fragments and arranging them into a pattern
4. Comparing the DNA markers or fragments from different sources
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The amplification process has been improved to enable the use of much
smaller DNA samples.
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DNA Matching
http://fig.cox.miami.edu
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Establishment of Paternity
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In cases involving the establishment of paternity, blood typing can ruleout some possibilities, but it cannot conclusively determine who is the
father of conception.
Comparing DNA samples from the mother, child, and purported father
can definitively establish paternity.
Recently, it was shown that Thomas Jefferson (the third U.S. President)
or a close relative fathered at least one of the children of his slave, Sally
Hemings.
http://www.foxnews.com
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Genomics
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Genomics, the science of studying genomes, was established in the past
20-25 years.
The initial focus was on pathogenic bacteria, which cause pneumonia and
meningitis.
H. influenzae (not the flu virus) contains about 1.8 million nucleotides and
1,709 genes.
Genome = an organism’s complete set of genes.
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Expanding Research
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More complex organisms, with much larger genomes, were subsequently
studied for their DNA sequences.
By 2003, the genomes of more than 100 organisms had been sequenced.
Researchers completed the sequencing of the human genome within the
past few years.
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Journal Covers
http://www.molgenmpg.de
http://genome.imim.es
http://biology.iupui.edu
http://www.bioinfo.mbb.yale.edu
The progression of complexity in genome research is shown
on scientific journal covers—sea urchin, mosquito, mouse,
and human.
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Human Genome Project
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The human genome has about 3.2 billion nucleotide pairs and 25,000 to
35,000 genes.
The Human Genome project, undertaken by an international consortium
of government-funded research groups, is completed and has published
much of its data.
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http://genome.imim.es
Why It’s Important
The understanding of the human genome sequence opens many
possibilities for medical diagnoses and treatments.
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Challenges
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An understanding of the human genome is a challenge due to its large
size, and because only relatively small segments of DNA code for mRNA
and tRNA.
Much of human DNA consists of repetitive patterns of the nucleotides (A,
C, G, T).
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Repetitive Patterns
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Segments of DNA containing thousands of base repetitions occur at the
centromeres and ends of chromosomes, possibly providing structural
support.
Other repetitive patterns, consisting of several hundred nucleotides, are
found between individual genes.
The markers often used in DNA fingerprinting are the repetitive patterns
since they are unique to the individual.
http://genome.wellcome.ac.ak
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Gene Therapy
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Human gene therapy uses recombinant DNA to treat some types of
disorders and diseases.
Gene therapy might be used to correct a genetic disorder—possibly
permanently, or in other instances just long enough to treat a medical
problem.
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Process
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The process involves taking a normal gene from a donor, and isolating
and cloning it using recombinant DNA technology.
The gene of the recombinant DNA is inserted into a vector—usually a
non-harmful virus.
The virus is injected into the patient—the gene the inserts itself into the
DNA.
The newly-introduced gene is transcribed and translated to produce the
desired protein.
Bone marrow stem cells—that produce cells for the blood and immune
system—are good candidates for gene therapy.
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http://www.em1.molmed.uni-erlangen.de
Fetal Gene Therapy
The University of Southern California
is a pioneer in gene therapy—the
research is conducted a few miles
from the ELAC campus.
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Safety
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Early concerns, included that recombinant DNA technology could create
deadly new microbes, are being addressed by national governments.
Laboratories must adhere to strict guidelines to prevent microbes from
being accidentally released.
They must adhere to strict procedures
to prevent worker contamination and
infection.
The microbes are genetically-crippled
so that cannot reproduce and survive
outside the laboratory.
Potentially dangerous experiments
have been banned.
Science fiction film from the early-1970s
http://thisdistractedglobe.com
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Food Concerns
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Genetically-modified strains are a sizeable portion of some agricultural
crops, including wheat and corn.
Crops have been genetically-engineered for higher yield, and resistance
to insects, viral diseases, and drought.
Some people fear genetically-modified plants could be harmful to human
health or the environment.
Another concern is that genetically-modified crops might pass their genes
to similar species in nearby wild areas or to adjacent farms that rely on
natural growing methods.
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Controversy
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The European Union suspended the introduction of new GM crops, and
is considering the banning of GM foods.
The U.S. National Academy of Sciences issued a report that geneticallymodified crops do not pose any health or environmental risks.
The debate is unlikely to subside any time soon due to a clash of world
views.
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Ethical and Moral Issues
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DNA technology raises legal, ethical, and moral questions—often with
few clear answers.
Should genetic engineering of gametes and zygotes be permitted to
breed for desirable physical characteristics in human children?
Should we allow genetic changes that could be beneficial today, but
possibly detrimental to the long-term health and survival of a species?
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More Ethical and Moral Issues
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Should we record the DNA fingerprint of every person, possibly as
early as birth?
Should employers and insurance companies be allowed to screen
job applicants for potentially harmful genes?
Should we take on a creator role for producing offspring including
humans?
The list of questions is long—the issues need debate and careful
deliberation by society.
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Words and Terms to Know
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DNA fingerprinting
E. coli bacteria
Fetal gene therapy
Gene therapy
Genetically-modified food
Genetically-modified organism
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Genomics
Human genome
Marker
Recombinant DNA
Transgenic organism
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Possible Test Items
5. Describe how synthetic insulin is synthesized using recombinant DNA
technology.
6. Describe gene therapy, and how knowledge of viruses and the transcription and translation processes are applied.
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