Transcript chapter15_Sections 5

Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 15
Biotechnology
(Sections 15.6 - 15.10)
Albia Dugger • Miami Dade College
15.5 Genomics
• Genomics provide insights into human genome function
• Full genome sequencing is now available, but it will be a long
time before we understand all the coded information
• genomics
• The study of genomes
• Includes whole-genome comparisons, structural analysis
of gene products, and the study of small-scale variation
Comparing Genomes
• Comparing genomes of different organisms shows evidence
of evolutionary relationships, and is used in medical research
• This is a region of the gene for a DNA polymerase:
DNA Profiling
• DNA profiling identifies a person by their DNA
• Examples of DNA profiling include determining an individual’s
array of SNPs on microscopic arrays, and analysis of short
tandem repeats using PCR
• In a criminal investigation, a short tandem repeat profile is
called a DNA fingerprint
Key Terms
• DNA profiling
• Identifying an individual by analyzing the unique parts of
his or her DNA
• short tandem repeats
• In chromosomal DNA, sequences of 4 or 5 bases
repeated multiple times in a row
SNP: Chip Analysis of a Genome
• This entire chip tests for
550,000 SNPs
• Each spot is a region
where the individual’s
DNA has hybridized
with one SNP
A Short Tandem Repeat Profile
• Each peak represents one short tandem repeat – the size of a
peak indicates the number of repeats at that locus
ANIMATION: Automated DNA sequencing
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ANIMATION: DNA fingerprinting
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ABC Video: Personalized Health Care
15.6 Genetic Engineering
• Genetic engineering produces a genetically modified
organism (GMO)
• A gene may be altered and reinserted into an individual of the
same species
• A gene from one species may be transferred to another to
produce an organism that is transgenic
Key Terms
• genetic engineering
• Process by which deliberate changes are introduced into
an individual’s genome
• genetically modified organism (GMO)
• Organism whose genome has been modified by genetic
engineering
• transgenic
• Refers to a genetically modified organism that carries a
gene from a different species
Engineered Microorganisms
• The most common GMOs are bacteria and yeast
• Bacteria have been modified to produce medically important
proteins such as insulin
• Engineered bacteria also produce enzymes used in food
manufacturing, such as chymotrypsin
A GMO
• E. coli modified to
produce a fluorescent
protein from jellyfish
ABC Video: Picking Your Baby’s Gender;
Selecting Sex Causes Controversy
15.7 Designer Plants
• Genetically engineered crop plants are widespread in the US
• Researchers use a Tumor-inducing (Ti) plasmid from bacteria
as a vector to transfer foreign or modified genes into food
crop plants such as soybeans, squash, and potatoes
• Transgenic crop plants may be resistant to diseases, offer
improved yields, or make a protein (Bt) toxic to insect larvae
Using the Ti Plasmid to
Make a Transgenic Plant
Using the Ti Plasmid to
Make a Transgenic Plant
A A Ti plasmid is
B The bacterium
inserted into an
infects a plant cell
Agrobacterium
and transfers the Ti
tumefaciens bacterium.
plasmid into it. The
The plasmid carries a plasmid DNA
foreign gene.
becomes integrated
into one of the cell’s
chromosomes.
C The plant cell
divides, and its
descendants
form an embryo.
D The embryo
develops into a
transgenic plant.
E The transgenic
plant expresses the
foreign gene. This
tobacco plant is
expressing a firefly
gene.
Fig. 15.12, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
Fig. 15.12a, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
A A Ti plasmid
is inserted into an
Agrobacterium tumefaciens
bacterium. The plasmid
carries a foreign gene.
Fig. 15.12a, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
Fig. 15.12b, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
B The bacterium infects a plant
cell and transfers the Ti plasmid
into it. The plasmid DNA becomes
integrated into one of the cell’s
chromosomes.
Fig. 15.12ab, p. 229
Using the Ti
Plasmid to Make
a Transgenic
Plant
Fig. 15.12c, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
C The plant cell divides,
and its descendants form
an embryo.
Fig. 15.12c, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
Fig. 15.12d, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
D The embryo develops
into a transgenic plant.
Fig. 15.12d, p. 229
Using the Ti Plasmid to
Make a Transgenic Plant
Fig. 15.12e, p. 229
Using the
Ti Plasmid
to Make a
Transgenic
Plant
E The transgenic plant expresses
the foreign gene. This tobacco
plant is expressing a firefly gene.
Fig. 15.12e, p. 229
ANIMATION: Gene transfer using a Ti
plasmid
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Genetically Modified (Bt) Corn
• The Bt gene makes
genetically modified
corn plants insect
resistant
• Corn produced by
unmodified plants is
more vulnerable to
insect pests
More GMOs
• Transgenic crop plants engineered for drought tolerance and
nutrition are being developed for impoverished areas
• Example: Rice plants engineered to make β-carotene, a
precursor of vitamin A, in their seeds
• The most widely planted GMO crops include corn, sorghum,
cotton, soy, canola, and alfalfa engineered for resistance to
glyphosate, an herbicide
Concerns with GMOs
• The engineered gene for glyphosate resistance is appearing
in wild plants and in nonengineered crops, which means that
transgenes can (and do) escape into the environment
• Many people are opposed to any GMO crops, calling such
foods “Frankenfoods”
• GMO use is a controversial issue; read the research and form
your own opinions
ANIMATION: Transferring genes into plants
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15.8 Biotech Barnyards
• Genetically modified (GM) animals are invaluable in medical
research and other applications:
• GM mice are used in gene research, and as models of
human diseases
• GM animals make proteins that treat cystic fibrosis, heart
attacks, blood clotting disorders, and nerve gas exposure
• GM goats produce spider silk protein in their milk
• GM rabbits make human interleukin-2
• GM farm animals produce more meat or milk
Genetically Modified Animals
• The pig on the left is transgenic for a yellow fluorescent
protein; its nontransgenic littermate is on the right
Genetically Modified Animals
• Mira the transgenic goat
produces a human
anticlotting factor in her
milk
Genetically Engineered
Animals in Research
• Multiple pigments in
transgenic “brainbow
mice” allow researchers
to map complex neural
circuitry of the brain
• Fluorescence
micrograph shows
individual nerve cells in
the brainstem
Knockouts and Organ Factories
• Human donors for organ transplants are in short supply, and
donated organs are subject to rejection
• Genetically modified animals may one day provide compatible
organs and tissues for xenotransplantation into humans
• xenotransplantation
• Transplantation of an organ from one species into another
Key Concepts
• Genetic Engineering
• Genetic engineering, the directed modification of an
organism’s genes, is now a routine part of research and
development
• Genetically modified organisms are now quite common
15.9 Safety Issues
• Researchers didn’t know whether new technologies might
produce superpathogens or new, dangerous forms of life
• Safety guidelines minimize potential risks to researchers in
genetic engineering labs
• Government regulations limit release of genetically modified
organisms into the environment, but don’t guarantee against
accidental releases or unforeseen environmental effects
15.10 Genetically Modified Humans
• With gene therapy, a gene is transferred into body cells to
correct a genetic defect or treat a disease
• As with any new technology, potential benefits of genetically
modifying humans must be weighed against potential risks
• We as a society continue to work through the ethical
implications of applying new DNA technologies
Getting Better
• Gene therapy is now being tested as a treatment for heart
attack, sickle-cell anemia, cystic fibrosis, hemophilia A,
Parkinson’s and Alzheimer’s diseases, several cancers, and
inherited diseases of the eye, ear, and immune system
• gene therapy
• Transfer of a recombinant DNA into an individual with the
goal of treating a genetic defect or disorder
• Inserts an unmutated gene into an individual’s
chromosomes
SCID-X1
• SCID-X1 is a severe X-linked disorder of the IL2RG gene,
which codes for an immune-system receptor protein
• Affected children can’t fight infections, and only survive in
germ-free isolation tents
• In the 1990s, 20 boys with SCID-X1 were treated with gene
therapy: Researchers used a genetically engineered virus to
insert unmutated copies of IL2RG into cells taken from their
bone marrow – 18 were cured
Successful Gene Therapy
• Rhys Evans was born
with SCID–X1
• His immune system was
permanently repaired by
gene therapy
Getting Worse
• No one can predict where a virus-injected gene will insert into
a chromosome – if it interrupts a gene that controls cell
division, cancer can result
• Five of the 20 boys treated with gene therapy for SCID-X1
developed bone marrow cancer (leukemia), and one died
• A young man with another genetic disorder had a severe
allergic reaction to the viral vector – four days after gene
therapy treatment, his organs shut down and he died
Getting Perfect
• Using various methods to select the most desirable human
traits raises ethical issues
• Is it acceptable to genetically engineer cuter babies, or
“superhumans” with strength or intelligence? How about to
prevent obesity, aggressiveness, or homosexuality?
• eugenics
• Idea of deliberately improving the genetic qualities of the
human race
Key Concepts
• Gene Therapy
• Genetic engineering continues to be tested in medical
applications
• It also continues to raise ethical questions
Personal DNA Testing (revisited)
• Although a DNA test can reliably determine the SNPs in an
individual’s genome, it can't reliably predict the effect of those
SNPs on the individual
• Most human traits are polygenic, and many are also
influenced by environmental factors such as life-style