copyright © 2003 pearson education, inc. publishing as benjamin cummings restriction fragments of...

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


• 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


Figure 12.11B

1 2

Longer fragments

Shorter fragments


• 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


• 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


• 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


• 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


• These sheep carry a gene for a human blood protein that is a potential treatment for cystic fibrosis

Figure 12.16


• 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


• 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


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


• “Golden rice” has been genetically modified to contain beta-carotene

– This rice could help prevent vitamin A deficiency

Figure 12.18B


• 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


• 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


• 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

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