Genetic Engineering
Selective Breeding
•
Choosing animals/organisms with
desired characteristics to breed and
produce offspring
•
Goal: to pass desired traits to next
generation of organisms
•
Examples: Dogs, Cats, Farm animals
and Crop plants
Selective Breeding
•
Hybridization
-
Crossing dissimilar
individuals to bring together the BEST
traits of BOTH organisms
•
HOPEFULLY, offspring of cross are
HARDIER than either parent
•
Example: in Crop plants combine
disease resistant of one with food
-
producing capacity of another
Selective Breeding
•
Inbreeding
-
Continued breeding of
individuals with similar characteristics
•
Seeking to maintain desired characteristics of
organism are maintained over many
generations
•
Risk
-
Since members of breed genetically
similar; may increase chances of recessive
disease being expressed
•
First Cousins NOT ALLOWED to marry!
Selective Breeding
•
Increasing variation
-
breeders do so by
DELIBERATELY inducing mutations
(ultimate source of genetic variability)
•
Using mutagens to increase variability!
•
Examples: new bacterial strains (clean
up oil
-
WOW) or new kinds of flowers
•
Polyploidy
-
accepted in plants; more
than two chromosomal sets
DNA Manipulation
•
Until very recently, plant and animal
breeders were unable to modify the
genetic code of organisms
•
Forced to work with inherent variation
in nature
•
Even with addition of variation via
mutations, changes in DNA produced
were random and unpredictable
DNA Manipulation
•
TODAY, scientists can use their
knowledge of DNA structure and its
chemical properties to alter the
sequence of DNA
•
Techniques include: DNA extraction, cut
DNA into smaller pieces, identify DNA
sequence one base at a time as well as
make unlimited copies of DNA
Genetic Engineering
•
Genetic Engineering
-
making changes in the
DNA code of a living organism
–
1.
DNA extraction
-
cells are opened and DNA
is separated from other cell parts
–
2.
Restriction enzymes
-
proteins that
preferentially cut DNA at a specific nucleotide
sequence
–
3.
Gel electrophoresis
-
Load DNA onto an end
of a porous gel and apply an electric charge,
separating DNA fragments based on size
Recombinant DNA
•
Combining DNA from different
organisms/different sources
•
Using SAME restriction enzyme (cut and
paste), take a gene from one organism
and attach it to the DNA of another
organism
Cell Transformation
•
Transformation
-
A cell takes in DNA
from outside the cell. This external DNA
becomes part of the cell’s DNA
•
Plasmid
-
Foreign/transforming DNA
added to a small, circular DNA molecule
Cell Transformation
•
2 essential features:
–
1. Plasmid has DNA sequence serving as
an
origin of replication
; if plasmid gets
inside bacterial cell, sequence ensures
plasmid that it will be replicated
–
2. Contains
genetic marker
-
allows one
to distinguish bacteria
containing/transformed by plasmid vs.
those that have not
-
Antibiotic
resistence gene
Transforming Plant cells
Gel electrophoresis
•
After restriction digestion, a mixture of
DNA fragments (different sizes) is
loaded onto one end of a gelatin
material
•
An electric voltage is applied to the gel
•
DNA molecules (negatively charged
-
WHY?) move toward the positive end of
gel
Gel electrophoresis
•
The smaller the DNA fragment, the
faster (and further on the gel) it moves
•
Gel electrophoresis used to:
–
compare DNA sequences of different
organisms or different individuals within
species
–
Locate and identify one particular gene out
of millions of genes in individual’s genome
Using DNA sequence
•
Knowing organism’s DNA sequence, one
can do the following:
–
1. Study specific genes
–
2. Compare genes to other organisms
genes
–
3. Identify functions of different genes and
gene combinations
Reading DNA sequence
•
Small, single stranded DNA pieces placed
in test tube with DNA polymerase
•
A supply of all four “free” nucleotide bases
is then added, along with one “labeled”
base (label with fluorescent dye)
•
When DNA polymerase adds labeled base,
replication is terminated
Reading DNA sequence
•
When using all 4 “labeled” bases
-
each
with different fluorescent color
-
a series
of tiny DNA fragments is created
•
Separate fragments via gel
electrophoresis
•
Pattern of colored bands tells exact
sequence of bases in the DNA
Polymerase Chain Reaction
•
PCR
-
Making multiple copies of a
specific gene of interest; a photocopy
machine stuck on “print.”
–
1. At each end of DNA “gene of interest” is
placed a COMPLEMENTARY DNA sequence
(known as a “primer” priming DNA
replication; Start point of DNA polymerase!
–
2. DNA heated to high temperature to
separate two template strands
Polymerase Chain Reaction
–
3. Next, DNA solution is cooled, allowing
primers to ANNEAL to template strands
(single stranded DNA)
–
4. DNA polymerase starts making copies of
region between primers
–
5. NOW, primers themselves can then
serve as templates to AMPLIFY “gene of
interest” that lies between primer
sequences
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