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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Restriction fragments of DNA can be sorted by size
12.10 Gel electrophoresis sorts DNA molecules by size
Figure 12.10
Mixture of DNAmolecules ofdifferent sizes
Powersource
Gel
Glassplates
Longermolecules
Shortermolecules
Completed gel
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Scientists can compare DNA sequences of different individuals based on the size of the fragments
12.11 Restriction fragment analysis is a powerful method that detects differences in DNA sequences
Figure 12.11A
Allele 1 Allele 2
w
x
y
Cut
Cut Cut
z
y
DNA from chromosomes
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 12.11B
1 2
Longer fragments
Shorter fragments
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Radioactive probes are also used to make comparisons
Figure 12.11C
Radioactive, single-stranded DNA (probe)
Restriction fragmentpreparation
1
Restrictionfragments
Gel electrophoresis2
Blotting3 Filter paper
Probe
Radioactive probe4
Detection of radioactivity(autoradiography)
5
Film
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The polymerase chain reaction (PCR) can quickly clone a small sample of DNA in a test tube
12.12 The PCR method is used to amplify DNA sequences
Figure 12.12
InitialDNAsegment
1 2 4 8
Number of DNA molecules
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• DNA fingerprinting can help solve crimes
12.15 Connection: DNA technology is used in courts of law
OTHER APPLICATIONS OF DNA TECHNOLOGY
Figure 12.15A, B
Defendant’sblood
Blood fromdefendant’sclothes
Victim’sblood
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Recombinant cells and organisms are used to manufacture useful proteins
12.16 Connection: Recombinant cells and organisms can mass-produce gene products
Table 12.16
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• These sheep carry a gene for a human blood protein that is a potential treatment for cystic fibrosis
Figure 12.16
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
12.17 Connection: DNA technology is changing the pharmaceutical industry and medicine
Figure 12.17
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• New genetic varieties of animals and plants are being produced
– A plant with a new trait can be created using the Ti plasmid
12.18 Connection: Genetically modified organisms are transforming agriculture
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 12.18A
Insertion ofgene into plasmidusing restrictionenzyme and DNAligase
1
Agrobacteriumtumefaciens
Tiplasmid
T DNA
Restrictionsite
Introductioninto plantcells inculture
2
RecombinantTi plasmid
Plant cell
T DNAcarrying
new genewithin plant
chromosome
Regenerationof plant
3
Plant withnew trait
DNA containinggene for desired trait
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
• Techniques for manipulating DNA have potential for treating disease by altering an afflicted individual’s genes
– Progress is slow, however
– There are also ethical questions related to gene therapy
12.19 Connection: Gene therapy may someday help treat a variety of diseases
Figure 12.19
Cloned gene (normal allele)
1 Insertnormal geneinto virus
Viral nucleicacid
Retrovirus
2 Infect bonemarrow cellwith virus
3 Viral DNAinserts intochromosome
Bone marrowcell from patient
Bone marrow
4 Inject cellsinto patient
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
12.20 Connection: Could GM organisms harm human health or the environment?
RISKS AND ETHICAL QUESTIONS
Figure 12.20A, B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
12.21 Connection: DNA technology raises important ethical questions
Figure 12.21A-C