Download Selective Breeding and Genetic Engineering

Chapter 13
SELECTIVE BREEDING AND GENETIC
ENGINEERING
SELECTIVE BREEDING

Breeding organisms for specific characteristics
 Ex:

Pedigree Dogs, livestock, horses, plants
Two Types of Selective Breeding:
1)
2)
Hybridization – combines traits from two different
organisms of the same species
Inbreeding – maintains desired traits within a
population of a species
HYBRIDIZATION
The offspring from hybridization are most often
healthier than either parent
 Increases genetic variation in a population
 Reduces the risk of an offspring inheriting a
genetic disorder
 Example: Mutt dogs, Labradoodles, Maltipoos,
Burbank Potato
 Burbank Potato:

Created circa 1900’s by Luther Burbank
 End to Ireland’s Potato Famine
 Resistant to mold/disease, increased food
production

INBREEDING
Once a desired characteristic is created in a
population, inbreeding allows that
characteristic to be maintained over
generations
 Only happens inside a specific population of
organisms
 Increases chance of an offspring inheriting a
genetic disorder
 Limits variation in a species
 EX: Purebred pedigree dogs: Golden
Retrievers, Poodles

VARIATION

Breeders can increase genetic variation in a
population by inducing mutations which are the
ultimate sources of variability
A
mutation is ANY change in DNA
 Factors that cause mutations are called Mutagens
 Ex:

Chemicals, Radiation (such as UV radiation)
NOT ALL MUTATIONS ARE BAD!
 Mutations
that somehow benefit the organism and
increase the organisms chance of reproducing in
the wild or captivity may lead to evolution
GENETIC ENGINEERING
Other than using selective breeding, scientists
may directly change and play with DNA for
Genetic Engineering
 Basic idea: Remove the DNA from a few cells,
edit and change the DNA using test tubes and
lab chemicals, replace the altered DNA into new
cells and possibly place the new cells with
altered DNA into an organism

TOOLS AND TECHNIQUES

A variety of laboratory techniques and tools are
involved
Restriction Enzymes: Enzymes that cut DNA at specific
nucleotide sequences
 Gel Electrophoresis: organizes DNA fragments
according to size
 Recombinant DNA: Creating DNA molecules (plasmids)
with portions from more than one organism
 Polymerase Chain Reaction (PCR): Creating multiple
copies of a short segment of DNA in a test tube

RESTRICTION ENZYMES
Restriction enzymes are enzymes that are
naturally found
 They ‘recognize’ specific nucleotide sequences
of DNA and cut the DNA in a specific location
 EX: The restriction enzyme EcoR I cuts DNA in
the middle of the TTAA sequence

Scientists may use these enzymes to chop up DNA
fragments so they may isolate specific genes
 These genes may later be combine with DNA from
another source (such as bacteria), creating
Recombinant DNA

RESTRICTION ENZYME DIAGRAM
GEL ELECTROPHORESIS

This process organizes DNA according to size


The gel itself is about the size of a small paperback
book, looks like clear jell-o and is about ¼ inches
thick


Allows scientists to study and mutate specific sizes and
sequences of DNA
There are different gels for different purposes
Procedure
Put tiny DNA fragments in a small test tube
 Dye the DNA blue
 Inject the DNA into the “wells” with a pipette (a scientific
eye-dropper)

GEL ELECTROPHORESIS PROCESS CONT.


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Place gel in plastic box and
hook up “jumper cables”
Pass electric current
through gel
DNA moves (-) to (+)
because DNA is (-) charged
molecule
Small pieces move farthest
the fastest
This process may be
modified and used to
“read” DNA sequences too!
GEL ELECTROPHORESIS IMAGE
RECOMBINANT DNA




Once a desired sequence
of DNA has been isolated
and replicated (via PCR), it
may be fused into a
plasmid in a bacteria
A plasmid is a short
circular piece of DNA
naturally found in bacteria
Bacteria cells containing
recombinant DNA plasmids
will produce the proteins
coded for by the
Recombinant DNA
EX: Bacteria that produce
Human Insulin for
diabetics
POLYMERASE CHAIN REACTION (PCR)


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Once a desired segment of
DNA is isolated (via gel
electrophoresis), the DNA may
be replicated to produce
hundreds of thousands of
copies
These copies may be inserted
into bacteria plasmids to
create recombinant DNA
bacteria
PCR uses cycles of heating
and cooling in a test tube and
the DNA polymerase of a
special bacteria to produce
lots of copies
TRANSFORMATION

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When recombinant DNA plasmids are inserted into living
bacteria cells, the process is called transformation
These transformed bacteria cells can produce the proteins in
the plasmids and they reproduce very rapidly
Allows scientists to mass produce proteins to medical use
Ex: Human insulin and Human Growth Hormone
Genetic Markers allow scientists to locate cells in a colony
that contain the desired plasmids


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Genetic markers are genes that make the bacteria resistant to
specific antibiotics.
If a colony of bacteria are treated with the specific antibiotic, only
the ones that survive contain the desired plasmid
Bacteria transform pretty easily, plants cells is more difficult,
animal cells even more so, however, inserting recombinant
DNA into animal cells (such as human brain cells) is difficult.
This is the basic idea behind current Gene Therapy research
APPLICATIONS OF GENETIC ENGINEERING

Transgenic Organisms – organisms that contain genes
from other species

Examples:
Jellyfish Pig – See handout
 Livestock with extra Growth hormone genes,
 Bacteria that Produce hormones such as insulin and Growth
Hormone
 Transgenic plants make up about 50% of our food industry


Cloning – clones are members of a population of
genetically identical cells produced from a single cell


Bacteria colonies produced from a single cell are all clones
Multicellular animals have been cloned: Dolly the sheep,
Copy Cat etc.
CLONING PROCESS
A nucleus from the body cell of a donor organism
(the animal being cloned) is implanted into an egg
cell which has no nucleus (removed by the
scientist)
 Once the egg cell “senses” a complete set of
chromosomes in its nucleus, it begins to divide and
reproduce like any other fertilized egg
 This egg is then implanted into a Foster mother’s
uterus where it grows and develops into a normal
baby
 Interesting side note: Clones DO NOT live as long
as the organism they were cloned from….has to do
with being made from “old” DNA

CLONING DIAGRAM