Concept 13 4 Biotechnology Has Wide Applications Many
Concept 13. 4 Biotechnology Has Wide Applications Many medically useful products are being made using biotechnology. Insulin was the first to be made by recombinant DNA technology in E. coli.
Figure 13. 12 Human Insulin: From Gene to Drug
Concept 13. 4 Biotechnology Has Wide Applications Before giving it to humans, scientists had to be sure of its effectiveness: • Same size as human insulin • Same amino acid sequence • Same shape • Binds to the insulin receptor on cells and stimulates glucose uptake
Concept 13. 4 Biotechnology Has Wide Applications Pharming: production of pharmaceuticals in farm animals or plants • Example: Transgenes are inserted next to the promoter for lactoglobulin, a protein in milk. The transgenic animal then produces large quantities of the protein in its milk.
Figure 13. 13 Pharming An expression vector carrying a desired gene can be put into an animal egg, which is implanted into a surrogate mother. The transgenic offspring produce the new protein in their milk. The milk is easily harvested and the protein isolated, purified, and made clinically available for patients.
Concept 13. 4 Biotechnology Has Wide Applications Human growth hormone (h. GH) can now be produced by transgenic cows. • With only 15 such cows, we could supply h. GH for all the children in the world that suffer from pituitary dwarfism. An enzyme to treat Gaucher’s disease (inherited disorder that affects lipid breakdown in lysosomes) has been developed using transgenic carrot cells.
Cloning Plants: Single-Cell Cultures One experimental approach for testing genomic equivalence is to see whether a differentiated cell can generate a whole organism A totipotent cell is one that can generate a complete new organism Plant cloning is used extensively in agriculture © 2011 Pearson Education, Inc.
Figure 20. 17 Cross section of carrot root 2 -mg fragments Fragments were Single cells free in cultured in nutrient medium; suspension stirring caused began to divide. single cells to shear off into the liquid. Embryonic plant developed from a cultured single cell. Plantlet was cultured on agar medium. Later it was planted in soil. Adult plant
Cloning Animals: Nuclear Transplantation In nuclear transplantation, the nucleus of an unfertilized egg cell or zygote is replaced with the nucleus of a differentiated cell Experiments with frog embryos have shown that a transplanted nucleus can often support normal development of the egg However, the older the donor nucleus, the lower the percentage of normally developing tadpoles © 2011 Pearson Education, Inc.
Figure 20. 18 EXPERIMENT Frog embryo Frog egg cell Frog tadpole UV Less differentiated cell Fully differentiated (intestinal) cell Donor nucleus transplanted Enucleated egg cell Egg with donor nucleus activated to begin development RESULTS Most develop into tadpoles. Most stop developing before tadpole stage.
Reproductive Cloning of Mammals In 1997, Scottish researchers announced the birth of Dolly, a lamb cloned from an adult sheep by nuclear transplantation from a differentiated mammary cell Dolly’s premature death in 2003, as well as her arthritis, led to speculation that her cells were not as healthy as those of a normal sheep, possibly reflecting incomplete reprogramming of the original transplanted nucleus © 2011 Pearson Education, Inc.
Figure 20. 19 TECHNIQUE Mammary cell donor Egg cell donor 1 Cultured mammary cells 2 Egg cell from ovary 3 Cells fused 4 Grown in culture Nucleus removed Nucleus from mammary cell Early embryo 5 Implanted in uterus of a third sheep Surrogate mother 6 Embryonic development RESULTS Lamb (“Dolly”) genetically identical to mammary cell donor
Figure 20. 19 a TECHNIQUE Mammary cell donor 1 Cultured mammary cells Egg cell donor Egg cell from ovary 3 Cells fused 2 Nucleus removed Nucleus from mammary cell
Figure 20. 19 b Nucleus from mammary cell 4 Grown in culture Early embryo 5 Implanted in uterus of a third sheep Surrogate mother 6 Embryonic development RESULTS Lamb (“Dolly”) genetically identical to mammary cell donor
Since 1997, cloning has been demonstrated in many mammals, including mice, cats, cows, horses, mules, pigs, and dogs CC (for Carbon Copy) was the first cat cloned; however, CC differed somewhat from her female “parent” Cloned animals do not always look or behave exactly the same © 2011 Pearson Education, Inc.
Figure 20. 20
Problems Associated with Animal Cloning In most nuclear transplantation studies, only a small percentage of cloned embryos have developed normally to birth, and many cloned animals exhibit defects Many epigenetic changes, such as acetylation of histones or methylation of DNA, must be reversed in the nucleus from a donor animal in order for genes to be expressed or repressed appropriately for early stages of development © 2011 Pearson Education, Inc.
Concept 13. 4 Biotechnology Has Wide Applications Recombinant DNA technology has several advantages: • Specific genes can be targeted • Any gene from any organism can be introduced into any other organism • New organisms can be generated quickly Recombinant DNA technology has many applications in agriculture.
Figure 13. 14 Genetic Modification of Plants versus Conventional Plant Breeding
Table 13. 2
Concept 13. 4 Biotechnology Has Wide Applications Crop plants that make their own insecticides: • The bacterium Bacillus thuringiensis produces a protein (Bt) that kills insect larvae.
Concept 13. 4 Biotechnology Has Wide Applications • Bt is highly toxic but breaks down rapidly in the environment. • Genes for the toxin have been isolated, cloned, modified, and inserted into plant cells using the Ti plasmid vector. • Transgenic corn, cotton, soybeans, tomatoes, and other crops are being grown, and pesticide use is reduced.
Figure 13. 15 Transgenic Rice Rich in β-Carotene Crops with improved nutritional characteristics: Golden rice contains genes from daffodils or corn and a bacterium, for enzymes involved in β-carotene production. (Vitamin A precursor)
Figure 13. 16 Salt-tolerant Tomato Plants Crops that are tolerant of environmental conditions: Example: Plants that are salt-tolerant
Concept 13. 4 Biotechnology Has Wide Applications Concerns about genetically modified crops center on these claims: 1. Genetic manipulation is an unnatural interference in nature. 2. Genetically altered foods are unsafe to eat. 3. Genetically altered crop plants are dangerous to the environment.
Concept 13. 4 Biotechnology Has Wide Applications 1. Advocates of biotechnology point out that all crop plants have been manipulated by humans. 2. Since only single genes for plant function are inserted into crop plants, advocates contend they are safe for human consumption. § Genes that affect human nutrition may raise more concerns.
Concept 13. 4 Biotechnology Has Wide Applications 3. Concern over environmental effects centers on escape of transgenes into wild populations. § Example: If a gene for herbicide resistance were transferred to a closely related weed
Concept 13. 4 Biotechnology Has Wide Applications Widespread use of glyphosate on glyphosateresistant crops has resulted in selection of rare mutations in weeds that make them resistant to glyphosate. More than 10 resistant weed species have appeared in the United States.
- Slides: 28