GENETIC ENGINEERING
Chapter 13
CHANGING THE LIVING WORLD
13-1
SELECTIVE BREEDING

Selective breeding – (artificial selection)
Breeders select individuals with desirable traits to
breed.
 Offspring inherit desirable traits from parents
(hopefully).

SELECTIVE BREEDING
Luther Burbank used
selective breeding to
develop Shasta daisies,
a popular variety.
SELECTIVE BREEDING

Hybridization

Crossing dissimilar individuals to produce offspring
with “hybrid vigor”.
HYBRIDIZATION
A mule is a cross
between a horse
and a donkey.
SELECTIVE BREEDING

Inbreeding

Crossing similar individuals to maintain desired
traits.
INBREEDING
Inbreeding maintains
the desirable traits of
Labradors, but may
make the breed more
susceptible to disease
and physical
abnormalities.
Concept Map
Section 13-1
Selective
Breeding
consists of
Inbreeding
Hybridizatio
n
which crosses
which crosses
Similar
organisms
Dissimilar
organisms
for
example
for
example
Organism
breed A
Organism
breed B
Organism
breed A
whic
h
whic
h
Retains desired
characteristics
Combines desired
characteristics
INCREASING VARIATION

Inducing mutations increases variation in a
population.
Variation in a population is a good thing.
 Radiation and chemicals are used.

INDUCING MUTATIONS
Bacteria have been
induced to digest oil.
INDUCED MUTATIONS
Strawberries have been
induced to be polyploid
making bigger, sweeter
strawberries.
MANIPULATING DNA
13-2
GENETIC ENGINEERING

Making changes in the genetic code.
TOOLS OF MOLECULAR BIOLOGY
DNA Extraction lyses the
cells (detergent), then
separates the DNA from
protein histones using a
protease enzyme. Lastly the
DNA is precipitated.
TOOLS OF MOLECULAR BIOLOGY
Restriction Enzymes
cut DNA into fragments
at certain base
sequences. Restriction
enzymes only cut their
specific sequence.
Restriction Enzymes
Recognition sequences
DNA sequence
Restriction Enzymes
Section 13-2
Recognition sequences
DNA sequence
Restriction enzyme
EcoRI cuts the DNA
into fragments.
Sticky end
TOOLS OF MOLECULAR BIOLOGY
Gel Electrophoresis
Separates DNA
fragments based on
size. An electric
current pulls the
fragments across a gel
and produces a unique
“fingerprint”. Used in
forensics
Figure 13-6 Gel Electrophoresis
Power
source
DNA plus
restriction enzyme
Longer
fragments
Shorter
fragments
Mixture of DNA
fragments
Gel
USING THE DNA SEQUENCE
In DNA Sequencing
DNA polymerase and
fluorescent labeled
nucleotides determine
the order of bases in a
fragment.
Figure 13-7 DNA Sequencing
USING THE DNA SEQUENCE
In gene splicing
DNA is cut into
fragments and
pasted together to
create
recombinant DNA
USING THE DNA SEQUENCE
Polymerase Chain
Reaction (PCR)
makes unlimited
copies of a gene.
Figure 13-8 PCR
DNA polymerase adds
complementary strand
DNA heated to
separate strands
DNA fragment
to be copied
PCR
cycles 1
2
3
4
5 etc.
DNA
copies 1
2
4
8
16 etc.
CELL TRANSFORMATION
13-3
CELL TRANSFORMATION

When a bacterial cell takes in DNA from outside
the cell, the external DNA gets incorporated into
the bacterium’s own DNA.
Recombinant DNA has been made.
 The cell has been transformed. It will make a new
protein(s).

TRANSFORMING BACTERIA

Bacterial plasmids (circular DNA) are used to
produce human hormones (HGH, insulin, clotting
factor).
Plasmids are useful because they are readily taken in
by bacteria and they easily replicate within a cell.
 Also genetic markers in the plasmid help isolate
transformed cells from non-transformed cells.


Typically the gene for resistance to antibiotics is used as a
genetic marker. After transformation, the culture is treated
with an antibiotic to kill all non-transformed cells.
Figure 13-9 Making Recombinant DNA
Section 13-3
Recombinant
DNA
Gene for human
growth hormone
Gene for human
growth hormone
Human
Cell
Sticky
ends
Bacterial Cell
DNA
recombination
DNA
insertion
Bacterial
chromosome
Plasmid
Bacterial cell for
containing gene for
human growth
hormone
TRANSFORMING PLANT CELLS

Plant cells don’t readily take in external DNA.
Plant cells are grown in culture with their cells walls
removed.
 Then plasmids are directly injected into the cells or
carried into the cells with a bacterium.

Figure 13-10 Plant Cell Transformation
Section 13-3
Agrobacteriu
m tumefaciens
Gene to be
transferred
Recombinant
plasmid
Cellular
DNA
Inside plant cell,
Agrobacterium inserts part
of its DNA into host cell
chromosome
Plant cell
colonies
Transformed bacteria introduce
plasmids into plant cells
Complete plant is
generated from
transformed cell
TRANSFORMING ANIMAL CELLS
DNA is injected directly into egg cells.
 DNA can be carried into cells with viruses.

Once inside the nucleus, recombinant DNA can
replace a host cell gene making it possible to treat
disorders caused by single genes.
 This therapy is called “gene replacement”.


Ex: cystic fibrosis
Knockout Genes
Section 13-3
Recombinant
DNA
Flanking
sequences match
host
Host Cell
DNA
Target gene
Recombinant DNA replaces
target gene
Modified Host Cell
DNA
APPLICATIONS OF GENETIC
ENGINEERING
13-4
TRANSGENIC ORGANISMS

Transgenic organisms contain genes from
different species.
Transgenic bacteria produce human proteins.
 Transgenic animals grow faster and produce leaner
meat.
 Transgenic plants are more resistant to disease.


Foods obtained from transgenic organisms are
labeled “genetically modified”.
CLONING
A clone is a member
of a genetically
identical population.
In 1997 the first
mammal was
cloned, a sheep
named Dolly.
Figure 13-13 Cloning of the First Mammal
Section 13-4
A donor cell is taken
from a sheep’s udder.
Donor
Nucleus
These two cells are fused
using an electric shock.
Fused Cell
Egg Cell
The nucleus of the
egg cell is removed.
An egg cell is
taken from an
adult female
sheep.
Cloned
Lamb
The fused cell
begins dividing
normally.
Embryo
The embryo
develops normally
into a lamb—Dolly
Foster
Mother
The embryo is placed
in the uterus of a
foster mother.