Download 2.18 Answers

SECTION 2.18 QUESTIONS
(Page 148)
Understanding Concepts
1. Products that exist through the use of biotechnology are: penicillin; yogurt; cheese; silage; human insulin; human
growth hormone; blood factors for treating hemophilia; vaccines for hepatitis B, diphtheria, and bacterial meningitis;
erythropoietin for treating anemia; interferons for cancer treatments; macrophage-stimulating factor; gene-corrected
T-cell lymphocytes to treat ADA deficiency.
2. The silage process: corn, grasses, alfalfa # harvested # chopped # blown tightly into a silo # anaerobic
bacteria
digest sugars # lactic acid production # silage resists spoilage from other microorganisms
3. Recombinant DNA technology creates new DNA when fragments of DNA from two or more different organisms
are
spliced together. The bacteria serve as the factory: restriction enzymes cut bacterial plasmids so that new DNA can
be
inserted. The E. coli bacterium provides the plasmid that is used to incorporate and cultivate the gene sequence that
controls production of insulin. E. coli can produce substantial amounts of human insulin under suitable growing
conditions.
This insulin is separated from bacterial cells and purified.
4. Comparison of recombinant DNA technology and the use of viral vectors in gene therapy:
Recombinant DNA technology Viral vectors in gene therapy
Similarities Both applications involve the removal and insertion of genes.
Both applications involve the use of microorganisms.
Differences Restriction enzymes cut a gene
sequence from a bacterial plasmid
and replace it with genes that will
produce the desired product.
The bacterial host produces the new
product (e.g., human insulin) and it is
harvested for use.
66 Unit 2 Student Book Solutions NEL
Restriction enzymes cut a gene sequence from the
nucleic acid (RNA or DNA) of a virus and replace it with
genes that will produce the desired effect when the
altered virus is inserted into a human T-cell lymphocyte
(e.g., a new ADA gene is incorporated into the chromosome
of the human T-cell lymphocyte; the altered DNA is
replicated when the lymphocyte divides and all new
generations will carry the altered gene sequence).
Pesticides kill many organisms other than the targeted pests.
Residue lasts for hours or days and will enter the food chain,
killing natural predators.
Pests will develop an immunity to chemicals; many sprayings
will be necessary.
Children and pets don’t understand about washing hands;
chemicals will enter their bodies through mouths and eyes.
Spray crosses roads and contaminates neighbours’ gardens.
People with chemical sensitivities in area will be affected.
Research shows that some chemical pesticides may be
carcinogens.
5. Human insulin does not produce the side effects associated with insulin produced from pigs or cows. This
technology
is expensive and not yet universally available.
Applying Inquiry Skills
6. Students should produce a diagram similar to Figure 1 on page 145 of the Student Text.
Making Connections
7. Genetically altered viruses or bacteria involve relatively new technology. There is no way of completely predicting
the
effect of genetically engineered microorganisms on ecosystems and human health.
8. W riting a newspaper announcement of the successful use of viral vectors to treat ADA deficiency in 1990 is both a
creative and factual assignment. The following information should be included: who (a four-year-old girl with ADA
deficiency, a rare genetic disease); where (United States); when (1990); what (gene therapy requiring the isolation of
the normal ADA gene from human T-cell lymphocytes and a transfer method to insert the normal gene into affected
human immune cells); and why (normal ADA gene is incorporated into the chromosomes and successive generations
of lymphocytes behave normally, i.e., correction of gene defect). A graphic of the procedure should be included.
9. Many congenital diseases would benefit from gene therapy using viral vectors. For example, the gene sequence
responsible for cystic fibrosis has been mapped, and it is now technically possible to replace the defective genes
using
adenoviruses. Clinical trails have taken place for nine years without any success; some deaths have occurred.
Students
may identify the following issues of concern: high cost (dollars and lives); false hope for patients; the possibility of
mutations and side effects; concern for safeguards and legislation; extension of technology to other causes that may
not be as noble (e.g., used to correct trivial problems or creation of “super race”).
10. Viral vectors work well with multiplying cells, e.g., T-cell lymphocytes, liver, and skin cells. This procedure
does not
work well with cells that are not multiplying (spinal cord and brain cells) because the altered genes are passed on
only
through cell division. Neurological disorders such as spinal cord injuries, Parkinson’s, and Alzheimer disease must
rely
on other forms of gene transfer.
11. The biotechnology laboratory technician program is more specialized at U.S. colleges and technological
institutes
than at those in Canada. Typically, it is a two-year, associate degree course of study. Students receive extensive
laboratory
experience in documentation, instrumentation, chromatography, microbiology, fermentation, protein purification
methods, and recombinant DNA methodologies. Graduates of the program work in research and development
laboratories or in small-scale production facilities. More information is available on the Nelson Science W eb site.
12. Links are available on the Nelson Science W eb site to research EPO use.
Erythropoietin (EPO)
Description – glycoprotein
– stimulates the manufacture of red blood cells by a process known as erythropoiesis
– role is to maintain the number of red blood cells at an optimal level to provide sufficient
oxygen transport to cells and tissues via a feedback mechanism
– also stimulates the growth of stem cells in the bone marrow to become mature red blood cells
– if the body loses its ability to manufacture sufficient EPO, the optimal number of red blood
cells in the circulation can no longer be maintained and anemia results
– stimuli such as bleeding or moving to high altitudes trigger EPO release
Administration – injected on a recurring schedule into a vein or under the skin
Use by athletes – used by some distance runners, cyclists, and swimmers to enhance performance: it stimulates
red blood cell production, increasing oxygen transport to muscles and enhancing endurance
– urine test will detect different sugars attached by the cells used in the pharmaceutical industry
compared to the sugars attached by the cells of the human kidney
– blood test also determines presence of recombinant EPO
Medical uses – treatment of anemia in:
• kidney dialysis patients
• AIDS patients (caused by certain drugs like AZT)
• cancer patients (a side effect of chemotherapy)
– treatment of severe blood loss in Jehovah’s Witnesses (religion forbids them to receive blood
transfusions)
– in the future, may be used by stroke victims as EPO is also synthesized in the brain when
oxygen becomes scarce to help protect neurons from damage
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13. Links are available on the Nelson Science W eb site to research cystic fibrosis.
Cystic fibrosis
Description – genetic disease most often caused by a defect in a single gene
– most common genetic disease in Caucasians
– characterized by a tendency to chronic lung infection and an inability to absorb fats and
other nutrients from food
– it is estimated that one in every 2500 children born in Canada has CF
– at the turn of the century, the median age of survival (the age beyond which half the CF
population can be expected to live) of a person with CF was over 35.6 years of age
Treatment – tailored to individual needs and depends upon the stage of disease and organs involved:
• tapping or “clapping” the chest and the back vigorously
• mask therapy to help loosen the mucus which clogs the lungs
• taking pancreatic enzymes with all meals to aid digestion
• taking nutritional supplements and vitamins to promote good nutrition
• taking antibiotics in pill or inhaled form to ease congestion and protect against and fight
lung infection
• exercise
Gene therapy – potentially a life-saving treatment, which tackles the root cause of CF, rather than the
symptoms
– 1989: discovery of defective gene that causes CF
– 1990: CF cells corrected in the lab by adding normal copies of the gene
– 1993: successful gene treatment repairs defective CF cells in some people
– strategies:
• a modified adenovirus is used to deposit normal genes directly in damaged CF airway cells
via nose drops, flexible tube, or aerosol
• patients are monitored to detect whether the normal CF gene has turned on; if so, the gene
will produce a normal protein that is vital to the health of cells lining the respiratory tract
• treatments are not yet expected to improve lung function because only a small portion of
the airways is being treated
– problems:
• when the immune system detects the gene treatment as an “invader,” immune cells attack
and prevent effective gene transfer
• researchers are modifying the gene delivery vectors to find other ways to circumvent the
body’s multi-faceted defence systems, e.g., use of modified viruses, liposomes (fat capsules),
and synthetic vectors
• CF scientists must also determine the life span of affected lung cells and identify the
“parent cells” which produce CF cells
• they also must learn how long the gene treatment lasts and how often it will have to be
repeated
Reflecting
14. Personal opinions will vary. Any well-reasoned answer is acceptable.
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