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GENETIC
ENGINEERING
Chapter 13
Selective Breeding

Humans use selective breeding to pass desired
traits on to the next generation of organisms.

Allows only those animals
with desired characteristics
to produce the next
generation.

2 Types of Selective breeding:
1.
2.
Hybridization
Inbreeding
Hybridization

Hybridization – cross breeding non-similar
individuals that bring together the best traits
of both organisms.

Produces hybrids (mixed organisms) that are
often BETTER than either parent…


disease resistant plants
plants with higher food
producing capacity
Inbreeding

Inbreeding - continued breeding
of individuals with similar
characteristics

Used to maintain the desired
characteristic of an organism.


Ex Dog breeding (beagles, poodles, golden retrievers,
etc.)
Risks of inbreeding:

genetically similar breeds increase the likelihood of
passing on recessive alleles for genetic defects
Increasing Variation

Breeders can increase the genetic variation
in a population by causing mutations, which
are the ultimate source of genetic variability.

mutations are inheritable changes in DNA that
occur spontaneously


radiation or chemicals may be used
If lucky, breeders can produce a few mutants with
desirable characteristics that are not found in the original
population
Manipulating/ Changing DNA

Genetic engineering is used to make
changes in the DNA.


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First, the DNA is extracted/ removed from an
opened cell.
Restriction enzymes are then used to cut the
DNA at a specific section of nucleotides.
The fragments are then separated and analyzed
using gel electrophoresis (used to compare
genomes of different organisms)  this way
scientists can locate & identify single genes out of
millions in a genome.
Cutting DNA with Restriction Enzymes
Separating DNA with Gel Electrophoresis
DNA Sequencing

In DNA sequencing, a complementary DNA
strand is made using a small proportion of
fluorescently labeled nucleotides.
Cutting, Pasting, & Making Copies of DNA

Recombinant DNA is
produced by combining DNA
from different sources.


These DNA sequences are
joined by using enzymes to
splice/ squeeze the DNA
together
A polymerase chain reaction
(PCR) allows biologists to
make many copies of a
particular gen

A few dozen cycles of PCR can
produce millions of copies of a
DNA sequence
During Cell Transformation, a cell incorporates/ includes foreign DNA into
its own DNA. A plasmid (circular DNA) is made, and contains a genetic marker,
which distinguishes the human DNA from the bacterial DNA. One way to make
recombinant DNA is to insert a human gene into bacterial DNA. The new
combination of genes is then returned to a bacterial cell, and the bacteria can
produce the human protein.
Knock-Out Genes

Recombinant DNA
can replace a gene in
an animal’s genome.
When recombinant
DNA is inserted into
the target location,
the host cell’s original
gene is lost or
“knocked out” of its
place.
Applications of Genetic Engineering

Transgenic Organisms: organisms that contain
some genes from other organisms
Transgenic Organisms are the basis
for Biotechnology!!!


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Transgenic bacteria now produce a host of important
substances useful for health & industry.
 Human insulin, growth hormone, and clotting factor
are now produced by transgenic bacteria.
Transgenic animals have been used to study genes and
improve the food supply.
 These animals often grow faster and produce LESS
fatty meat.
Transgenic plants are an important part of our food
supply.
 Many transgenic plants produce a natural
insecticide, so the crops do not have to be sprayed
with pesticides.
Cloning – a member of a population of
genetically identical cells produced from a single
cell.
Cloning…Meet Dolly the Sheep!!!