Chapter 13 Gene Technology

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Transcript Chapter 13 Gene Technology

Chapter 13 Gene Technology
The majority of DNA is the same
in all humans.
Only about 0.10 % of an
individual’s genome is different.
How can scientists identify
people based on the very small
differences in their DNA
molecules?
This chapter explores
manipulating DNA for scientific
& practical purposes.
Some DNA Technology Vocabulary
• Polymorphisms- variations in the length of the
DNA molecule between genes (occurs in the noncoding “junk” DNA)
• VNTR- variable number tandem repeats.
These are short repeating sequences- like CACACAthat repeat a variable number of times behind each other
(in tandem).
** This # of repeats is what is different in individuals & is
what forensic scientists look at in DNA profiling.
Polymerase chain reaction- lab technique that
copies DNA fragments
• Restriction enzyme- bacterial proteins
(enzymes) that recognizes a specific sequence of DNA
& always cuts DNA at specific sequences
• Gel Electrophoresis-
technique that separates
molecules (like proteins or nucleic acids) according to
size & electrical charge. Exposed on X-ray film.
• DNA fingerprint- The resulting pattern of bands
on gel electrophoresis
• Genetic Engineering- process of altering
genetic material or cells or organisms & that makes
them into new substances.
• Recombinant DNA- results when DNA from 2
different organisms is joined.
• Clone-
(noun) is an exact copy of a DNA segment,
whole cell or complete organism.
(verb) to make a genetic duplicate.
• Plasmid- small rings of DNA found naturally in
some bacterial cells.
• Vector- any agent, such as a plasmid or virus, that
can carry a DNA molecule from 1 organism to
another. (Also means Intermediate host. Examplemosquito is a vector for malaria pathogen)
I. DNA Technology
A. DNA Identification
Main steps:
1. Isolate the DNA molecule from cells, make copies
(-Polymerase chain reaction- copies DNA)
2. Cut the DNA into shorter fragments
-Restriction enzymes (enzymes always cut at
specific nucleotide sequences- so scientists know
what ends of fragments look like.)
3. Separate fragments by size
- Technique is gel electrophoresis
4. Compare patterns of DNA sample to a known
DNA sample treated in the same way.
Electrophoresis matches DNA from a crime scene (7) with that of a suspect (4).( www.fathom.com)
B. Useful applications of splicing DNA
1. Forensics- used DNA “fingerprint” to ID criminals
2. Used to ID remains of victims of accidents,
crimes, fires, etc.
3. Trace human evolution- migration over time
sampling bones, remains, etc
4. Making Recombinant DNA
- new capabilities for microorganism- insert gene for
an enzyme or hormone into genome of bacteria- they
produce insulin, HGF & many other medicines, drugs
& medically important proteins. Also, commercial
products like corn, anti-fungal plants, enzyme for
cheese, etc made this way.
History of Forensic Testing
from Invention & Technology Fall 2006
DNA Takes The Stand by J. Kelly
1. 1880s - French policeman, A. Bertillon -11
measurements
-included arm span, cheek width, sitting height,
and right-ear length. Combined, they could identify
a person with precision.
-Odds slim that two persons would have identical
values for a range of measurements.
-Approach was considered scientific - both precise
and systematic
2. By- 1920s. -a simpler,
faster, more useful method :
the fingerprint.
-In 1892 - Englishman Francis Galton determined
that finger prints were unique to individuals and
permanent through a person’s life.
- Secretions left on items a person touched could
contain a record of his fingerprints and later be used
to connect him with a crime scene.
- Galton’s way of classifying the various patterns is
still used today.
3. ABO Blood typing
-1901. Karl Landsteiner discovered incompatible types of
blood formed clumps & prevented transfusion.
Labeled types A, B, AB, & O.
-If a criminal left behind type A blood at the scene,
suspects with the other blood types were ruled out.
-But a large portion of the population shared that blood
type –this evidence could only exclude suspects; it was
not specific enough to erase reasonable doubt.
http://mac122.icu.ac.jp/gen-ed/mendel-gifs/17-abo-blood-test.JPG
The story of how the genetic code became a
revolutionary tool for law enforcement.
• In English village- early 1980s-2 murders & rapes of 15 year old
English schoolgirls- police & villagers wanted answers.
• Investigation was centered on a “slow” 17 year old hospital
worker, who, under intense interrogation, confessed to killing
one, not both. But prosecutors were convinced he was lying.
They needed to link him conclusively to both crimes.
• Dr. Alec Jeffreys, a professor of genetics at the nearby University
of Leicester, had developed a way to identify unique chemical
attributes in samples of deoxyribonucleic acid.
• Turning DNA testing into a forensic tool was no easy matter
because 99.9 percent of human DNA is the same for everyone
• Dr. Jeffreys used VNTR sequences- (parts of junk DNA that
repeat & are where the individual differs)
• After rigorous lab work, Dr. Jeffery thought-“there is something
wrong with the technology”. Test showed that one man had
indeed raped both girls. But, in spite of his confession, the youth
in custody was not the culprit.
• The police then took the unprecedented step of requesting blood
from more than 4,000 local men. Samples from those whose
blood type matched that of the evidence—about 10 percent—
were subjected to Jeffreys’s DNA analysis.
• Break came when a woman overheard a conversation at the
bakery about one man falsely giving a sample for a coworker.
They brought in the co-worker & he was a match with the DNA
at the crime scene.
• It exonerated an innocent man and helped police make their case
against a guilty one.
• 1986 -used in America to convict a Florida rapist. Methods with
restriction enzymes similar but improved by New York company
• To find out lots more- go to
www.inventionandtechnology.com
Summing up DNA testing
1. Scientists/Detectives take blood sample
– From crime scene & from suspects
2. Long strands of DNA are extracted from
the cell, copied & cut up into pieces using
enzymes.
3. Process pieces using gel electrophoresis.
4. Analyze results
Go to this website to practice catching a criminal;
http://www.pbs.org/wgbh/nova/sheppard/analyze.html
II. The Human Genome Project
A. Mapping the human genome
- research effort to sequence all of
the 3.3 billion nucleotides of the
human genome
-determine location of every gene
on every chromosome.
- found 98% of DNA does not
code for any proteins (“junk
DNA”) (Therefore, only 2%
codes for proteins)
Goals from website
http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
• identify all the approximately 20,000-25,000 genes
in human DNA,
• determine the sequences of the 3 billion chemical
base pairs that make up human DNA,
• store this information in databases,
• improve tools for data analysis,
• transfer related technologies to the private sector,
and
• address the ethical, legal, and social issues (ELSI)
that may arise from the project.
A. Mapping the human genome continued
-Scientists had originally estimated that there were
about 100,000 genes but found only 30-40,000
genes.
-found additional uses of RNA in addition to
translation.
-There are about 8 million single nucleotide
polymorphisms (places where individuals
differ by only 1 nucleotide- are important for
DNA fingerprinting.)
B. Other specieshave also mapped
genome of
bacteria like
E.coli, fungi,
plants & animals
such as Fruit flies,
& dogs.
III. Genetic Engineering
A. Medical applications- gene therapy, cloning,
vaccines
B. Agricultural applications
C. Bioethical Questions- Who own the information. (see
article p269 & page 2 of this sheet.)
• Bioethics- is the study of ethical issues related
to DNA technology.
-Should private companies own information about specific
genes?
-How do we stop misuse of information- by
government, employers, schools, insurance agencies,
agricultural & medical personnel?
Genetic Medical Applications
• Making medicine- until recently- medicine had to be
collected from plants or made from chemicals. Now
can make body substances like human blood clotting
factors, insulin, vaccines & HGH with GM bacteria.
• Making body parts- may be able to clone cells &
make new organs so that no rejection occurs. May
be able to grow new human liver in another organism
like a pig.
• May also be able to screen for diseases, create
“designer babies”, cure cancer.
Gene Therapy
• Example: replace or repair faulty
gene for cystic fibrosis.
• Insert a copy of good gene from
healthy person into virus.
• Infect patient’s lungs with virus,
virus delivers good gene. Now
patient can make the right protein
to stop accumulation of mucus &
can breathe normally.
Imagine being this mother of/or child with CF,
Daily you must massage & loose mucus.
Any cold could overwhelm & cause death.
Now imagine what gene therapy represents.
OHSU RESEARCHERS PRODUCE FIRST
GENETICALLY MODIFIED MONKEY
January 11, 2001
• Oregon Health Sciences University
report the world's first genetically
modified nonhuman primate - an
important step toward designing and
perfecting new treatments for human
genetic disorders.
• By developing cloned, genetically
modified and stem-cell-derived primate
models, scientists will be able to carefully
and rigorously test the most innovative
therapies, using the fewest animals, so
that these treatments are perfected and
optimized before being used to treat
humans."
– promotion of beneficial insects
http://www.ohsu.edu/unparchive/2001/011001monkey.shtml
Release of genetically
modified (GM) mosquitoes
• vector-borne diseases like malaria and dengué are among the
most serious and prevalent infectious diseases worldwide.
• GM mosquitoes may offer an alternative strategy to current
methodologies
(which are stalling because of drug resistance, absence of
vaccines and
inadequate mosquito control techniques.)
• GM mosquitoes are resistant to pathogen
infection and transmission, but the public-health
and environmental consequences of releasing
such insects are unclear,
mainly because of a lack of knowledge of the
ecology and population biology of mosquitoes.
Cloning- How It Works
1. Egg has nucleus(with its DNA) removed
2. Cell from organism to be cloned,
such as a skin cell, is collected.
3. Empty egg & whole skin cell are
placed closed together & electric
shocked, which makes them fuse together.
4. The new cell contains DNA from only
1 cell (the skin cell, not the egg) & is
grown
It becomes a new baby.
Making Insulin:
1. Isolate Gene
The gene for producing HUMAN insulin protein is isolated. The gene is part
of the DNA in a human chromosome. The gene can be isolated and then
copied so that many insulin genes are available to work with.
2. Prepare Target DNA
In 1973, two scientists named Boyer and Cohen developed a way to take
DNA from one organism and put it in the DNA of bacterium.
3. Insert DNA into Plasmid
With the plasmid ring open, the gene for insulin is inserted into the plasmid
ring and the ring is closed. The human insulin gene is now recombined with
the bacterial DNA plasmid.
4. Insert Plasmid back into cell
5. Plasmids multiply
6.
7 Cells Produce Proteins
Millions of people with diabetes now take human insulin produced
by bacteria or yeast (biosynthetic insulin) that is genetically
compatible with their bodies, just like the perfect insulin produced
naturally in your body.
First GM food- A tomato
• The first commercially grown genetically
modified food crop, a tomato, was made
more resistant to rotting, by adding a gene.
• 1994- Approved by FDA –decided it did not constitute a
health hazard, and did not need special labeling. Calgene
was allowed to release it into the market.
• Welcomed by consumers who purchased the fruit at two
to five times the price of standard tomatoes.
• Company bought by Monsanto in 1995.
– Monsanto Company is a multinational agricultural
biotechnology corporation & is the world's leading producer
of the herbicide Roundup.
– Monsanto is also by far the leading producer of genetically
engineered (GE) seed, holding 70%–100% market share for
various crops.
Examples: Featherless chicken
• Scientists have bred a
controversial featherless
chicken which they say is
faster growing.
• The birds, created at the
Hebrew University in Israel,
will not need to be plucked,
saving money in processing
plants.
• they would not be suitable for
cooler countries,but OK in hot
climates
• There was a rumor that KFC
uses these already but it is
not true.
http://news.bbc.co.uk/1/hi/sci/tech/2000003.stm
Fishy Strawberries
Flounder is a fish that can withstand
icy cold temperatures.
Scientists took the gene in the fish that
Produces an antifreeze & inserted it into
a plasmid of a bacterium
The bacterium infected the strawberry &
the flounder antifreeze gene entered the
strawberry’s DNA
The new GM strawberry cells are grown
Into new plants that have strawberries
which make a protein that keeps the fruit
from frost damage.
www.usbornequicklinks.com
Genetically Engineered Bt Corn
• soil bacterium Bacillus thuringiensis
(Bt) is a natural pesticide.
• Scientists isolated the blueprint for a
protein within the bacteria's DNA.
This protein kills insects. ·
• Bt gene combined with DNA of corn.
• The makeup and heredity of the corn
was changed. The Bt protein that kills
insects is now made by the corn plant.
• Some studies show Monarch
butterflies are killed by the corn.
• Concerns that this may cause some
species to become extinct.
http://www3.iptv.org/exploreMore/ge/main.cfm
• Biotechnology is a vital issue that impacts all of
us.
• Largely between 1997 and 1999, gene-modified
(GM) ingredients suddenly appeared in 2/3rds of
all US processed foods. This food alteration was
fueled by a single Supreme Court ruling. It
allowed, for the first time, the patenting of life
forms for commercialization.
Risks of GM foods
• Is the food safe to eat? (new chemicals)
• The risk of gene transfer to weeds.
• Crop biodiversity, worries about "gene pollution"
& ecology
– Lesson from other non-native plant species have been
introduced to environments to provide food, feed, fiber, &
timber, but have disrupted local fauna & flora.
– (but-keep in mind that alien crop introduction accounts for about
95% of the crop area in the United States )
• Concern about horizontal transfer of genes from
GM crops to other organisms, such as bacteria
Potential positive impact of
GM crops
• Increased crop yield for hungry people.
• Improved environments
– decreasing agricultural expansion to preserve
wild ecosystems;
– improving air, soil, and water quality by
promoting reduced tillage,
– reducing chemical and fuel use;
– improving biodiversity through resuscitation of
older varieties and