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Ch 13: Genetic Engineering
13-1 Changing the Living World
A. Selective Breeding
1. For thousands of years, people have bred animals and plants that have desired traits. This technique is
called selective breeding.
2.
Humans use selective breeding, which takes advantage of naturally occurring genetic variation, to
pass desired traits on to the next generation of organisms.
3. One tool used by selective breeders is hybridization.
a. In hybridization, individuals with different traits are crossed
b. The goal is to produce offspring that have the best traits of both parents. These offspring, called
hybrids, are often hardier than the parents
4. Breeders use inbreeding to maintain a group of plants or animals with desired traits.
a. In inbreeding, individuals with similar traits are crossed.
b. A disadvantage of inbreeding is the risk of bring together two recessive alleles for a genetic
defect.
Activity: Selective Breeding 
Identify the parents a breeder would select in order to breed offspring with the traits listed. The first one has
been done for you.
- A breeder breeds rabbits 2 and 8. What trait is the
breeder most likely interested in?
A:
Answers 
2&7
4&8
1&6
B. Increasing Variation
1. Selective breeding would be nearly
impossible without large amounts of variation
in traits
2.
Breeders can increase the genetic variation
in a population by inducing mutations
3. Mutations- inheritable changes in DNA
a. Mutations do occur naturally
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b. Breeders can boost the rate of mutation through use of radiation and chemicals
c. Many mutations are harmful
d. However breeders can produce useful mutations
4. The use of mutations is particularly useful with bacteria
a. Their small size enables millions of organisms to be treated with radiation or chemicals at the
same time
b. Using this technique, scientists have been able to develop hundreds of beneficial strains,
including bacteria that can clean up oil from oil spills
5. New varieties of plants have also been developed using mutants
a. If chromosomes fail to separate, extra sets of chromosomes result. This is called polyploidy.
b. In animals, polyploidy is usually fatal
c. In plants, the new species that result are larger and stronger than their diploid relatives
13-2 Manipulating DNA
A. The Tools of Molecular Biology
1. To increase variation, scientists can also make changes directly to the DNA molecule.
2. Genetic engineering- the intentional changing of an organism’s DNA
3.
Scientists use their knowledge of the structure of DNA and is chemical properties to study and
change DNA molecules
4. Extracting DNA
a. Scientists can extract, or separate, DNA from other cell parts using a chemical procedure
5. Cutting DNA
a. Scientists can cut DNA into smaller pieces using restriction enzymes
6. Separating DNA
a. Scientists use gel electrophoresis, a method in which DNA fragments are put at one end of a
porous gel.
b. When an electric current is applied to the gel, DNA molecules move toward the positive end of
the gel.
c. This technique allows scientists to compare the gene composition of different organisms or
different individuals.
Activity: Restriction Enzymes; EcoR I 
A restriction enzyme cuts DNA at a specific
sequence of nucleotides. The enzyme EcoR
I cuts a DNA strand when it encounters the
nucleotide sequence CTTAAG.
Circle the places on the DNA strand where
EcoR I would recognize and cut the DNA.
Note: There may be more than one
nucleotide sequence on each DNA strand.
The first one has been done for you…
Ans:
B. Using the DNA Sequence
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1. Reading the Sequence
a. Scientists can also read the order of nucleotide bases in a DNA fragment
b. They make a copy of a single strand of DNA with colored nucleotides inserted at random places.
c. Reading the order of the colored bands in a gel gives the nucleotide sequence of the DNA
fragment
2. Cutting and Pasting
a. Scientists can change DNA sequences
b. Short sequences of DNA made in the laboratory can be joined to the DNA molecule of an
organism
c. DNA from one organism can be attached to the DNA of another organism
d. These DNA molecules are called recombinant DNA because combining DNA from different
sources makes them
3. Making Copies
a. Scientists often need many copies of a certain gene to study it.
b. A technique called polymerase chain reaction (PCR) allows scientists to do that
c. PCR is a chain reaction which DNA copies become templates to make more DNA copies
13-3 Cell Transformation
A. Introduction
1. DNA fragments do not work by themselves. They must be part of the DNA molecule in an organism
2.
During transformation, a cell takes in DNA from outside the cell. This external DNA becomes a
component of the cell’s DNA
3. Bacterial, plant and animal cells can be transformed
B. Transforming Bacteria
1. To add DNA fragments to bacteria, the fragment is placed in a plasmid.
2. Plasmid- a small, circular DNA molecule that occurs naturally in some bacteria
3. Scientists join the fragment to the plasmid by cutting both with the same restriction enzymes
a. The cut pieces join because the ends match up
4. When scientists transform bacteria, not all bacteria take in the plasmid.
5. Scientists can identify those bacteria that carry the plasmid because the plasmid also carries a genetic
marker.
Activity: Bacterial Transformation 
Use the words below to label the diagram
Foreign DNA, plasmid, recombinant DNA, transformed bacterium
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- Why might a scientist insert a gene
that codes for a human growth
hormone into bacteria cells?
A:
13-4 Applications of Genetic
Engineering
A. Transgenic Organisms
1. Scientists wondered if genes
from one organism could
work in a different organism.
2. Some scientists isolated the
gene from fireflies and
inserted it into a plant gene.
The plants glowed in the
dark.
3. This showed that both plants
and animals use the same
process to translate DNA into
proteins.
4. The glowing plant is
transgenic because it has a
gene from another species
5.
Genetic engineering has
spurred the growth of biotechnology, which is changing the way we interact with the living world.
6. Some examples of genetic engineering include:
a. Human genes have been added to bacteria.
i. These transgenic bacteria are used to make human proteins such as insulin, human
growth hormone, and clotting factor
b. Scientists have made transgenic animals to study the role of genes and to improve food supply
i. Transgenic animals may be used to supply us with human proteins that can be collected
in the animal’s milk
c. Transgenic plants that can make their own insecticide have been formed
i. Others are resistant to weed killers
ii. Some have been engineered to contain vitamins needed for human health
B. Cloning
1. Clone- a member of a population of genetically identical cells that were produced from a single cell.
2. clones are useful in making copies of transgenic organisms
3. It is easy to produce cloned bacteria and plants
4. Animals are difficult to clone
5. In the 1990s, scientists in Scotland successfully cloned a sheep
a. Animal cloning has risks
b. Studies suggest that cloned animals may have genetic defects and other health problems
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