Download Manipulating DNA extracting and studying DNA

Chapter 13
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Selective breeding is used to produce
organisms with desired traits.
◦ How could this be accomplished?
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Two methods used to selective breed are
hybridization and inbreeding.
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Crossing parent organisms with different
forms of a trait produces offspring that are
considered hybrids (Bb).
Hybridization is selecting specific traits that
will give hybrid organisms a competitive edge.
◦ Ex. To be more disease resistant, produce more
offspring, or to even grow faster
◦ A disadvantage of hybridization is that it is time
consuming and expensive; however, often the
advantages outweigh the disadvantages.
What are some possible advantages?
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Once a desired trait has been produced, the
process of inbreeding is utilized to ensure it is
passed to future generations.
Inbreeding- process in which 2 closely related
organisms are bred to have the desired traits
and to eliminate the undesired ones.
A disadvantage of inbreeding is that harmful
recessive traits can also be passed on to
future generations.
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Once a breeder observes the desired trait, the
genotype must be determined.
A test cross is done to determine genotype.
Test cross- breeding an organism that has an
unknown genotype with one that is
homozygous recessive for the desired trait.
◦ How would this be helpful?
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What comes to mind with the phrase “genetic
engineering”?
Researchers use genetic engineering to
manipulate DNA.
Genetic engineering- manipulating DNA of
one organism in order to insert exogenous
DNA (DNA of another organism)
Copying the Gene Sequence
 Polymerase Chain Reaction (PCR) is a technique
used to make many copies of a desired gene.
 Steps to PCR
1. DNA strands are separated by heating.
2. Short pieces of DNA, called primers, are
attached to the DNA strands to prepare a
place for DNA polymerase to start copying.
3. These copies serve as templates for more
copies.
Changing DNA
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Recombinant DNA Technology
 Joining together DNA from two or more sources.
 This makes it possible to change the genetic
composition of living organisms.
 DNA of one organism is extracted and cut into pieces.
 A piece that produces a desired protein is inserted into
another organism’s DNA.
 The organism with the new piece of DNA produces the
desired protein.
Tool/Process
Function
Application
Restriction enzymes
Cut DNA strands into
fragments
Used to create DNA
fragments with sticky ends
or blunt ends that can join
with other DNA fragments
Gel electrophoresis
Separates DNA fragments by
size
Used to study DNA
fragments of various sizes
Recombinant DNA
technology
Combines DNA fragment
with DNA from another
source
Used to create recombinant
DNA to be used to study
individual genes and
genetically engineered
organisms
Gene cloning
Produces large numbers of
identical recombinant DNA
Used to create large
amounts of recombinant
DNA to be used in
genetically engineered
organisms
DNA sequencing
Identifies DNA sequence of
cloned recombinant DNA
molecules
Used to identify errors in
DNA sequence and to
compare other genes
Polymerase Chain Reaction
Makes copies of regions of
DNA
Used to copy DNA for study
and medical testing
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It is the use of genetic engineering to find
solutions to problems.
Genetically engineered organisms that have
genes inserted from another organism are
called transgenic organisms.
◦ Transgenic animals- mice and fruit flies used for
research; livestock to improve food supply; goats to
produce proteins called antithrombin III to prevent
human blood from clotting during surgery
◦ Transgenic plants – to be resistant to insect and
other pests
◦ Transgenic bacteria – used to make insulin, growth
hormones, etc..
Some examples of GM Animals include:
1.
Recombinant Bovine Growth Hormone
increases milk production in dairy cows.
2.
Pigs modified to produce more lean meat.
3.
Salmon injected with growth hormone to
grow faster.
4.
Chicken injected with estrogen which
increases breast size.
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Preventing Disease
◦ Provitamin A rich Golden Rice will hopefully prevent
problems caused by infant malnutrition.
◦ Transgenic plants and animals to produce human
antibodies.
◦ Transgenic sheep and pigs to produce human
proteins.
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Medical Research
◦ Transgenic animals with human immune systems for
researching cures and organ growth for transplants.
Safety of Transgenics
• Pros of GM Foods
• Careful studies of GM foods have provided no scientific support
for concerns about their safety , and it does seem that foods
made from GM plants are safe to eat. (At least that is what the
companies marketing the products claim. The other side doesn’t
have enough money or the research facilities to undergo such
large scale research.)
• Cons of GM Foods
• GM foods are not required to undergo special safety testing
before entering the market.
• No additional labeling is required to identify a product as
genetically modified.
1.
Artificially introduced proteins may cause allergic reactions in
people with allergies.
2.
Recombinant Bovine Growth Hormone (rGBH) increases udder
infection causing milk to contain increased levels of pus, fat, and
bacteria. Antibiotics are given to the cows and then passed to their
milk and consumed by people causing antibiotic resistant bacteria
to thrive.
3.
rBGH causes increased production of another hormone which at
high levels can cause cancer.
4.
Herbicide and pesticide resistant crops are over sprayed with weed
killer causing everything but the crop to die. The crops then absorb
the weed killer which is passed on to the consumer who eats the
crop.
5.
Destruction of plant life surrounding the crops destroys the habitats
of many beneficial insects and the animals that survive on the
insects such as birds.
6.
Seeds of genetically modified plants are unable to reseed
themselves naturally so the farmer must purchase new seeds when
it is time to replant.
7.
GM foods have been linked to ADD, ADHD, earlier onset of puberty in
females, inability to concentrate, cancer, etc.
8.
The hormone estrogen is changing puberty and physical appearance
of male and female adolescents.
Ethics of New Biology
• Just because we have the technology to modify and
organism’s characteristics, are we justified in doing so?
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Human DNA is made up of approximately 3
billion nucleotides.
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The HGP wanted to identify all of those genes.
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Although the protein-coding regions of DNA
are almost identical among individuals, the
noncoding regions are very unique. DNA
fingerprinting involves separating these DNA
fragments to observe distinct banding
patterns that are unique to individuals.
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A defective protein is replaced with a good one,
eliminating the symptoms of the disease.
Insertion of a new “healthy” gene into the organism
to provide needed (usually) proteins, hormones etc.
Gene is carried into the host by a viral
vector (like the flu virus) that has been disabled.
Can provide relief for many genetic diseases.
Gene therapy research is ongoing with cystic
fibrosis, gout, rickets, sickle-cell anemia, and
inherited high cholesterol.
Problems: immune responses to the virus,cancer