Transcript 12.11 Restriction fragment analysis is a powerful method that

12.10 Gel electrophoresis sorts DNA molecules by
size
• Restriction fragments of DNA can be sorted by
size
Mixture of DNA
molecules of
different sizes
Longer
molecules
Power
source
Gel
Shorter
molecules
Glass
plates
Completed gel
Figure 12.10
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12.11 Restriction fragment analysis is a powerful
method that detects differences in DNA
sequences
• Scientists can
compare DNA
sequences of
different
individuals based
on the size of the
fragments
Allele 1
Allele 2
w
Cut
z
x
Cut
y
Figure 12.11A
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Cut
y
DNA from chromosomes
1
2
Longer
fragments
Shorter
fragments
Figure 12.11B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Radioactive
probes are
also used to
make
comparisons
1
Restriction fragment
preparation
Restriction
fragments
2
Gel electrophoresis
3
Blotting
4
Radioactive probe
Filter paper
Radioactive, singlestranded DNA (probe)
Probe
5
Detection of radioactivity
(autoradiography)
Film
Figure 12.11C
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12.12 The PCR method is used to amplify DNA
sequences
• The
polymerase
chain reaction
(PCR) can
quickly clone a
small sample
of DNA in a
test tube
Initial
DNA
segment
1
2
4
Number of DNA molecules
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8
Figure 12.12
OTHER APPLICATIONS OF DNA
TECHNOLOGY
12.15 Connection: DNA technology is used in courts
of law
• DNA fingerprinting can help solve crimes
Defendant’s
blood
Blood from
defendant’s
clothes
Victim’s
blood
Figure 12.15A, B
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12.16 Connection: Recombinant cells and
organisms can mass-produce gene products
• Recombinant cells and organisms are used to
manufacture useful proteins
Table 12.16
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• These sheep
carry a gene for a
human blood
protein that is a
potential
treatment for
cystic fibrosis
Figure 12.16
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12.17 Connection: DNA technology is changing the
pharmaceutical industry and medicine
• Hormones, cancer-fighting drugs, and new
vaccines are being produced using DNA
technology
– This lab equipment
is used to produce
a vaccine against
hepatitis B
Figure 12.17
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12.18 Connection: Genetically modified organisms
are transforming agriculture
• New genetic varieties of animals and plants are
being produced
– A plant with a new trait can be created using the
Ti plasmid
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Agrobacterium
tumefaciens
DNA containing
gene for desired trait
1
Ti
plasmid
T DNA
Insertion of
gene into plasmid
using restriction
enzyme and DNA
ligase
Plant cell
2
Recombinant
Ti plasmid
Restriction
site
Introduction
into plant
cells in
culture
3
Regeneration
of plant
T DNA
carrying
new gene
within plant
chromosome
Plant with
new trait
Figure 12.18A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• “Golden rice” has been genetically modified to
contain beta-carotene
– This rice could help prevent vitamin A
deficiency
Figure 12.18B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
12.19 Connection: Gene therapy may someday
help treat a variety of diseases
• Techniques for
manipulating DNA have
potential for treating
disease by altering an
afflicted individual’s genes
Cloned gene (normal allele)
1 Insert
normal gene
into virus
Viral nucleic
acid
Retrovirus
2 Infect bone
marrow cell
with virus
– Progress is slow, however
3 Viral DNA
inserts into
chromosome
– There are also ethical
questions related to gene
therapy
Bone marrow
cell from patient
Bone
marrow
4 Inject cells
Figure 12.19
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into patient
RISKS AND ETHICAL QUESTIONS
12.20 Connection: Could GM organisms harm
human health or the environment?
• Genetic engineering involves
some risks
– Possible ecological damage
from pollen transfer between
GM and wild crops
– Pollen from a transgenic variety
of corn that contains a pesticide
may stunt or kill monarch
caterpillars
Figure 12.20A, B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
12.21 Connection: DNA technology raises
important ethical questions
• Our new genetic knowledge
will affect our lives in
many ways
• The deciphering of the
human genome, in
particular, raises
profound ethical issues
– Many scientists have
counseled that we
must use the
information wisely
Figure 12.21A-C
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings