Applications and Ethics of Genetic Engineering and Biotechnology Chapter 19 Applications and Ethics of Genetic Engineering and Biotechnology Susan Chabot Honors Genetics Lemon Bay High School

Genetically Engineered Organisms Synthesize a Wide Range of Biological and Pharmaceutical Products Figure 24-1 (a) Humulin, a recombinant form of human insulin, was the first therapeutic protein produced by recombinant DNA technology to be approved for use in humans. (b) To synthesize recombinant human insulin, synthetic oligonucleotides encoding the insulin A and B chains were inserted (in separate vectors) at the tail end of a cloned E. coli lacZ gene. The recombinant plasmids were transformed into E. coli host cells, where the -gal/insulin fusion protein was synthesized and accumulated in the cells. Fusion proteins were then extracted from the host cells and purified. Insulin chains were released from -galactosidase by treatment with cyanogen bromide. The insulin subunits were purified and mixed to produce a functional insulin molecule. Figure 24.1

Table 24-1 Some Genetically Engineered Pharmaceutical Products Now Available or under Development

Recombinant DNA Approaches for Vaccine Production and Transgenic Plants with Edible Vaccines Figure 24-2 To make an edible vaccine, a gene from a pathogen (a disease-causing agent, such as a virus or bacterium) is transferred into a vector, which is then introduced into plant cells. In this example, infection of banana plant leaf segments transfer the vector and the pathogen’s gene into the nuclei of banana leaf cells. The leaf segments are grown into mature banana trees that express the pathogenic gene. Eating the raw banana produced by these plants trigger s an immune response to the protein encoded by the pathogen’s gene, conferring immunity to infection by this pathogen. Figure 24.2

Genetic Engineering of Plants Has Revolutionized Agriculture

Figure 24-4 (a) A recent analysis of nearly 800 transgenic crop trials worldwide shows that GM varieties of corn, soybean, cotton, alfalfa, and wheat are among the most commonly manipulated crops ( Nature Biotechnology, 23(3), p. 281, March 2005). (b) During the past 10 year s, transgenic crops have been rapidly adopted in both industrialized and developing countries (Ernst & Young, Beyond Borders: Global Biotechnology Report 2006, www.ey.com/beyondborders).

Figure 24-5 (a) Glyphosate is the active chemical in Roundup, a commonly used herbicide. (b) A weed-infested glyphosate-resistant soybean plot before (left) and after Roundup treatment (right).

Figure 24-6 To create glyphosate-resistant transgenic plants, the EPSP synthase gene from bacteria is fused to a promoter such as the promoter from the cauliflower mosaic virus. This fusion gene is then ligated into a Ti-plasmid vector, and the recombinant vector is transformed into an Agrobacterium host. Agrobacterium infection of cultured plant cells transfers the EPSP synthase fusion gene into a plant-cell chromosome. Cells that acquire the gene are able to synthesize large quantities of EPSP synthase, making them resistant to the herbicide glyphosate. Resistant cells are selected by growth in herbicide-containing medium. Plants regenerated from these cells are herbicide-resistant.

Figure 24-7 (a) Golden rice, a str ain genetically modified to produce  -carotene, a precursor to vitamin A. Many children in countries where rice is a dietary staple lose their eyesight because of diets deficient in vitamin A. (b) White rice lacks the enzyme phytoene synthase, which is responsible for converting C20 into phytoene, a rate-limiting step in the production of -carotene. Introducing the phytoene synthase gene into rice is one way to overcome this block and produce golden rice enriched in -carotene.

Figure 24-8 Transgenic Atlantic salmon (bottom) overexpressing a growth hormone (GH) gene display rapidly accelerated rates of growth compared to wild strains and nontransgenic domestic strains (top). GH salmon weigh an average of nearly 10 times more than nontransgenic strains.

Figure 24-9 Transgenic cows for battling mastitis Figure 24-9 Transgenic cows for battling mastitis. The mammary glands of nontransgenic cows are highly susceptible to infection by the skin microbe Staphylococcus aureus. Transgenic cows express the lysostaphin transgene in milk, where it can kill S. aureus before they can multiply in sufficient numbers to cause inflammation and damage mammary tissue.

Figure 24-10 GloFish, marketed as the world’s first GM-pet, are a controversial product of genetic engineering.

Genetic Engineering and Genomics Are Transforming Medical Diagnosis Genetic Tests Based on Restriction Enzyme Analysis

Figure 24-11 For amniocentesis, the position of the fetus is first determined by ultrasound, and then a needle is inserted through the abdominal and uterine walls to recover amniotic fluid and fetal cells for genetic or biochemical analysis.

10 -12 weeks

Figure 24-14 A single cell from an early-stage human embryo created by in vitro fertilization can be removed and subjected to preimplantation genetic diagnosis (PGD) by ASO testing. DNA from each cell is isolated, amplified by PCR with primers specific for the gene of interest, then subjected to ASO analysis as shown in Figure 24–13. In this example, a region of the -globin gene was amplified and analyzed by ASO testing to determine the sickle-cell genotype f or this cell. Figure 24.14