1. 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

2. 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
Cut y y
Figure 12.11A
DNA from chromosomes

3. 1 2
Longer fragments
Shorter fragments
Figure 12.11B

4. Radioactive probes are also used to make comparisons1
Restriction fragment preparation
Restriction fragments 2
Gel electrophoresis
Filter paper 3
Blotting 4
Radioactive probe
Radioactive, single- stranded DNA (probe)
Probe 5
Detection of radioactivity (autoradiography)
Film
Figure 12.11C

5. 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 8
Number of DNA molecules
Figure 12.12

6. 12.15 Connection: DNA technology is used in courts of law
OTHER APPLICATIONS OF DNA TECHNOLOGY
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

7. 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

8. These sheep carry a gene for a human blood protein that is a potential treatment for cystic fibrosis
Figure 12.16

9. 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

10. New genetic varieties of animals and plants are being produced
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

11. Agrobacterium tumefaciens
DNA containing gene for desired trait
Plant cell 1 2 3
Ti plasmid
Recombinant Ti plasmid
Insertion of gene into plasmid using restriction enzyme and DNA ligase
Introduction into plant cells in culture
Regeneration of plant
T DNA
T DNA carrying new gene within plant chromosome
Plant with new trait
Restriction site
Figure 12.18A

12. “Golden rice” has been genetically modified to contain beta-carotene
This rice could help prevent vitamin A deficiency
Figure 12.18B

13. Cloned gene (normal allele)
Connection: Gene therapy may someday help treat a variety of diseases
Cloned gene (normal allele)
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 1
Insert normal gene into virus
Viral nucleic acid
Retrovirus 2
Infect bone marrow cell with virus 3
Viral DNA inserts into chromosome
Bone marrow cell from patient
Bone
marrow 4
Inject cells into patient
Figure 12.19

14. RISKS AND ETHICAL QUESTIONS
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

15. 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