Chapter 13 Genetic Engineering - nvohl

Chapter 13


Genetic Engineering


Changing the Living World

Selective Breeding

•
Humans use
selective breeding
, which
takes advantage of naturally occurring
genetic variations.

–
Domestic animals

–
Farm animals

–
Crop plants

•
Pass
desired traits

to the next generation

Hybredization

•
Luther Burbank may have been the greatest
selective breeder of all time (1849
–

1926)

–
Used
Hybredization

crossing dissimilar
individuals to bring out the best in each

–
Combined the disease resistance of one plant
with the food
-
producing capacity of another

–
The result was a new line of plants that allowed
farmers to increase food production

Inbreeding

•
The continued
breeding
of individuals with
similar characteristics

–
Breeds of dogs such as beagles and poodles

•
Risks

–
Chance that
two recessive alleles

form a
genetic defect

•
Joint problems with German shepherds for example


Increasing Variation

•
Selective breeding is possible because of
the
wide variation

found in natural
populations

•
Breeders increase the variation by
inducing
mutations

(mutations are the cause of
variations)

•
With luck over a number of attempts
desirable traits may be found.

Increasing Variation 2

•
Because of the small size of bacteria,
radiation or chemical treatment may
produce some of the bacteria with useful
characteristics.

–
Bacteria that digest oil

–
Bacteria that produce hydrogen


Increasing Variation 3

•
Producing new kinds of plants

–
Prevent chromosomal separation

–
Sometimes produce cells that have two to three
times the number of chromosomes

–
Called
polyploidy

the extra chromosomes in
plants sometimes make them larger and
stronger.

–
Polyploidy is fatal in animals

Manipulating DNA

•
Scientists have broken the DNA code

–
They study the structure of DNA and its
chemical properties.

–
Techniques are used to extract DNA from cells
and cut it into smaller pieces and identify the
sequence of bases in a DNA molecule and
make unlimited copies.


Manipulating DNA

•
Tools

–
DNA extraction

–

chemicals can separate the
DNA from other cell parts.

–
Cutting DNA

–

Restriction enzymes

are
known and each one cuts DNA at a specific
sequence of nucleotides.


–
DNA fragments

can be separated using
gel
electrophoresis.

A DNA fragment is placed at
one end of a porous gel, and voltage applied.
DNA molecules, which are negatively charged
move to the positive end of he gel.

–
The sequence can then be read.


Applications of Genetic
Engineering

•
Transgenic Organisms
–

It is possible to
construct organisms that are
transgenic,
meaning that they contain genes from other
species. The transformed cells grow new
organisms.

•
Transgenic microorganisms
–

transgenic
bacteria now produce substances that form
proteins cheaply and in great quantities.

–
ie. Insulin, growth hormone, and clotting factor

Cloning

•
A
clone

is a member of a population of
genetically identical cells produced from a
single cell.