Transcript Selective Breeding

Genetic Engineering
and
Selective Breeding Notes
Selective Breeding:
Breeding Plants and Animals for
the Benefit of Humans
Selective Breeding: Selecting individuals with desired
traits to produce offspring for the next generation
a.
b.
c.
Used to produce most crops (corn, wheat…)
Used to produce all breeds of domestic animals –
dogs, horses, cats, sheep, cattle
Also called artificial selection
All of the different plants produced from wild
mustard by selective breeding!
Luther
Burbank
(1849-1926)
developed
over 800
varieties of
plants.
Limits of Selective Breeding
1. It
can be a slow process, taking lots of
time and many generations to get the
traits that you want.
2. Can
not mix traits from two different
species
3. Can
result in undesirable offspring or
traits
a. Example: Might want plants that
are drought resistant; however,
end up with drought resistant
plants that don’t produce many
seeds!
Two Types of Selective Breeding:
1. Inbreeding
Inbreeding: crossing two individuals with similar
traits.
•
Advantages:
1.
Desired trait is enhanced and preserved
through many generations
•
Disadvantages:
1.
Decreases genetic variation which could lead
to vulnerability to disease
2.
Homozygous recessive traits that are
unwanted or unhealthy are more likely to show
up.
Disadvantages of Inbreeding
Because of the loss
of genetic variation
within this crop, all
were equally
vulnerable to disease.
This entire crop
was wiped out in
weeks by one
disease!
Two Types of Selective Breeding:
2. Hybridization
Hybridization: crossing 2 dissimilar, but related
organisms
1.
Offspring called hybrids
•
Advantages:
1.
Usually stronger/hardier than parents –
2.
known as hybrid vigor
•
Disadvantages:
1.
May promote the loss of native species if
released into the wild.
Hybridization Examples
1. African catfish
(left) grows faster
than Thai catfish.
2. Thai catfish
(middle) has better
tasting flesh than
African catfish.
3. Hybrid (right)
grows fast & has
good tasting flesh.
Problem: It has been released into rivers of
Thailand and is disrupting food chains.
Other hybrids:
The horse and donkey are mated to produce a mule.
The lion and tiger are breed to produce a Liger or Tigon.
The horse and zebra are mated to produce a zorse
Genetic engineering: changing
an organism’s DNA to make it
more beneficial to humans
Genetic Engineering:
Recombinant DNA and Transgenic Organisms
1.
Recombinant DNA: DNA made from two
separate species
a.
2.
A gene from one organism is “recombined”
with another organisms DNA.
Transgenic Organism: any organism that
contains recombinant DNA.
a.
These new gene combinations could
never be possible in nature
Transgenic Plants
Researchers isolate a gene from an organism that has
the trait they want to give to a plant.
and cells are grown
Just for Fun?- a glowing tobacco plant
http://archives.cbc.ca/IDD-1-75-1597/science_technology/genetically_modified_food/
What’s Next on Your Plate?
What genes do we
want them to have?
•Insect, Herbicide, and
Fungal resistance
•Drought resistance
•Product quality
•New vitamins or other
nutritional benefits
•Longer Shelf Life
(Flavr Savr Tomato)
Transgenic Organisms: Plants
Example: Rice plants and daffodils can not
cross pollinate with each other in nature.
The rice on the right is
called Golden Rice.
Its genome contains the
gene for producing
vitamin A from
daffodils.
This rice is healthier for
people who do not get
enough vitamin A in
their diets.
Transgenic Organisms: Animals
Animals are now being produced with genes that
increase milk production and muscle mass (meat).
Problem: unhealthy; legs cannot support weight
Transgenic Organisms: Animals
1. Genetically
engineered mice used
in cancer research:
Contain gene from glowing jellyfish
b. Glow when a cancer is growing in
them
c. Mice are given chemotherapy
drugs; if the tumor shrinks, they
glow less & less
Mice don’t die from the cancer or the
chemotherapy drugs
a.
2.
Mice expressing “glow”
gene from jellyfish.
Glowing jellyfish
http://www.pbs.org/wgbh/nova/baby/
Transgenic Organisms: Bacteria
Used to produce important
medicines:
a.
Insulin for diabetics
b.
Human growth hormone
c.
Bacteria cultures
Anticoagulants for (for
treating heart attack
patients)
Insulin
Other Uses for Transgenic Bacteria
What’s Next?
The artificial sweetener in most
diet sodas phenylalanine is
already being made by
transgenic bacteria.
How about making a
transgenic bacteria that
when introduced to the
mouth, prevents cavities?
What about transgenic
bacteria able to clean up
oil spills?
Dangers of Transgenic Organisms
 Ethical
problem (should we)
 Transgenic bacteria could be used to
create biological weapons
 Insertion of gene may interfere with
workings of other genes causing disease
 A superior transgenic organism that
escaped into the environment may
damage the ecosystem (food chains)
Genetic Engineering
and the Future
Got Silk? Video
Spider silk in goat’s milk
Creating hybrids to study
evolutionary relationships
Hybrid form is
similar to
types found in
archeological
digs.
Hugh Iltis
Corn domestication started around 10,000 years ago in central America. Creating
hybrids between modern corn and the wild grass teosinte has produced fertilize
hybrids. Analyzing the genetic differences between the hybrids and parent stocks,
has shown that single gene mutations are responsible for:
•Changing a bushy phenotype (seen in teosinte) to a single stalk phenotype (corn)
•Turning teosinte seeds inside out—the hard outer casing became the central cob.