Transcript Selective Breeding

Chapter 15- Genetic Engineering
15.1
Selective Breeding
What is this??
Why did humans create this type of car??
Selective Breeding
◦
The differences among breeds of dogs
are great. Where did these differences
come from?
◦
@Humans use selective breeding to
produce animals with certain desired
traits.@ Selective breeding allows only
those animals with wanted characteristics
to produce the next generation.
Selective Breeding
◦
For thousands of years,
we’ve produced new varieties
of cultivated plants and nearly
all domestic animals by
selectively breeding for
particular traits.
◦
Native Americans selectively
bred teosinte, a wild grass
native to central Mexico, to
produce corn, a far more
productive and nutritious plant.
◦
There are two common
methods of selective
breeding—hybridization and
inbreeding.
How we’ve used Selection
b. Dogso
o
c.
Tiny Chihuahuas and Huge Great Danes
Labrador retrievers with short coats and poodles with
curly hair.
Humans are always looking to make animals that are
better hunters, better retrievers or more capable of
producing a quality product.
Hybridization
◦
American botanist Luther Burbank developed
more than 800 varieties of plants using selective
breeding methods.
◦
One method Burbank used was
@hybridization, crossing dissimilar
individuals to bring together the best of both
organisms.@
◦
Hybrids—the individuals produced by such
crosses—are often hardier than either of the
parents.
Hybridization
◦
Many of Burbank’s hybrid crosses
combined the disease resistance of one
plant with the food-producing capacity of
another.
◦
The result was a new line of plants that
had the traits farmers needed to increase
food production.
Inbreeding
◦
@To maintain desirable characteristics
in a line of organisms, breeders often use
inbreeding@, the continued breeding
of individuals with similar
characteristics.
◦
The many breeds of dogs are
maintained using inbreeding, ensuring
that the characteristics that make each
breed unique are preserved.
Inbreeding
◦
Inbred organisms are genetically very similar
and can increase the probability that
organisms may inherit genetic disorders.
Increasing Variation
◦
When scientists manipulate the genetic makeup of
an organism, they are using biotechnology.
◦
Biotechnology is the application of a
technological process, invention, or method to
living organisms.
◦
Selective breeding is one form of biotechnology
important in agriculture and medicine, but there are
many others.
Bacterial Mutations
◦ @Mutations occur spontaneously, but breeders can
increase the mutation rate of an organism by using
radiation or chemicals.@
◦
Many mutations are harmful to the organism, but
breeders can often produce a few mutants—individuals
with mutations—with useful characteristics that are not
found in the original population.
◦
For example, scientists have developed hundreds of
useful mutant bacterial strains by treating bacteria with
radiation or chemicals.
◦
Certain strains of oil-digesting bacteria are effective for
cleaning up oil spills, and scientists are currently working
to produce bacteria that can clean up radioactive
substances and metal pollution in the environment.
Polyploid Plants
◦
Drugs that prevent the separation of
chromosomes during meiosis are very useful
in plant breeding. These drugs can produce
cells that have many times the normal
number of chromosomes.
◦
Plants grown from these cells are called
polyploidy, they have many sets of
chromosomes.
◦
Polyploidy is usually fatal in animals, but
plants are much better at tolerating extra sets
of chromosomes.
Polyploid Plants
◦
@Polyploidy can quickly produce new
species of plants that are larger and stronger
than their diploid relatives.@
◦ A number of important crop plants, including
bananas, have been produced in this way.
Crossing individuals with different
traits to bring together their best
characteristics is called
a. domestication
b. inbreeding
c. hybridization
d. polyploidy
Crossing individual with similar
characteristics so that those
characteristics will appear in their
offspring is called
a. inbreeding
b. hybridization
c. recombination
d. polyploidy
Taking advantage of naturally
occurring variation in organism to
pass wanted traits on to future
generations is called
a. selective breeding
b. forensics
c. gene therapy
d. mutation