CH. 12

Explain how DNA technology has helped to treat, diagnose, & prevent disease.

2 products made using recombinant cells are human insulin & human growth hormone. Insulin, normally secreted by the pancreas, is a hormone that helps regulate the levels of glucose in the blood. The main sources of this hormone were slaughtered pigs & cattle. Although insulin extracted from these animals are chemically similar; it is not identical too human insulin & can therefore cause allergic reactions in some people. However, Humulin - human insulin produced by bacteria - became the first recombinant DNA drug approved by the U.S. FDA. Treatment with human growth hormone is a boon to children born with a form of dwarfism caused by inadequate amounts of this hormone. Because growth hormones from other animals are not effective in humans, children with HGH deficiency historically have had to rely on scarce, expensive supplies extracted from human cadavers. This enzyme is used to treat a rare human genetic condition called Gaucher's disease. One approach to vaccine production is the use of genetically engineered cells or organisms to produce large amounts of a protein molecule that is found on the pathogen's outside surface. This method has been used to make the vaccine against hepatitis B, a disabling & sometimes fatal liver disease. Another way to use DNA technology in vaccine development is to make a harmless, artificial mutant of the disease-causing pathogen by altering one or more of its genes. Genetic engineering rapidly transformed the field of medicine & continues to do so today.

Describe the benefits & risks of gene therapy in humans. Discuss the ethical issues that these techniques present.

Benefits: In people afflicted with disorders caused by a single defective gene, it might be possible to replace or supplement the defective gene by inserting a normal allele into that person's cells. Once there, the normal allele might be expressed, potentially offering a permanent cure after just one treatment. Risks: Although the gene therapy treatment cured the patients of SCID, there were some serious side effects: Four of the treated patients developed leukemia, and one died after the inserted gene turned the patient's blood cells cancerous. Some researchers see no difference between the transplantation of genes as described above & the transplantation of organs because neither act affects future generations. But the ethical questions become tricky when researchers contemplate the genetic manipulation of gamete-forming cells or zygotes, feats already accomplished in lab animals. Such tinkering would result in changes that are passed on to future generations, permanently altering the genetic lineage. Should we try to eliminate genetic defects in our children & their descendants? Some critics worry that tampering with human genes in this way will lead to eugenics, the deliberate effort to control the genetic makeup of human populations. From an evolutionary perspective, genetic variety is a necessary ingredient for the survival of a species as environmental conditions change with time. Genes that are damaging under some conditions may be advantageous under others (one example is the sickle-cell allele). Are we willing to risk making genetic changes that could be detrimental to our species in the future? We may face this question soon.

Describe the risks posed by the creation & culturing of GMOs & the safeguards that have been developed to minimize these risks.

Cancer, might be hazardous to humans & other organisms, lead to allergic reactions, diseased crops can easily pass gene to other good ones, may reduce genetic diversity which is necessary. Evaluated for potential risks, & possibly require a label.

Explain how genetically modified organisms (GMOs) are transforming agriculture.

Improve food production, pest resistance, & nutritional value of crops. Human proteins are made through genetically modifying plants. Can produce better meats by adding genes for fat metabolism or active hormone gene.

Explain how different organisms are used to mass-produce proteins of human interest. Note the advantages & disadvantages of each organism.

Recombinant plasmids are taken up by the bacteria through transformation. Then the bacteria reproduce & create clones of cells all containing the recombinant plasmids. The bacteria then produce the protein coded for by the donor DNA. From there harvested proteins can be used directly or genes may be inserted into other organisms. Human insulin molecules are now produced by this method. Genes are also inserted into the fertilized egg of some mammals and if they incorporate the desired gene they can make the desired protein in its milk which can then be extracted