3.) Explain why this gene is not harmful to humans and most other animals,
yet is able to kill caterpillars.
B.t. is practically non-toxic to humans and animals. Humans exposed orally to 1000 mg/day of B.t. showed no effects. B.t. does not persist in the digestive systems of mammals that ingest it. A wide range of studies have been conducted on test animals, using several routes of exposure. The highest dose tested was 6.7 x 10^11 spores per animal. The results of these tests suggest that the use of B.t. products causes few, if any, negative effects. B.t. was not acutely toxic in tests conducted on birds, dogs, guinea pigs, mice, rats, and humans. B. thuringiensis is harmful to caterpillars because the bacterial cells usually produce a spore and a crystalline protein toxin - called an endotoxin - as they develop. Most commercial B. thuringiensis products contain the protein toxin and spores, but some contain only the toxin component. When B. thuringiensis is ingested by a caterpillar, the protein toxin is activated by alkaline conditions and enzyme activity in the insect's gut. If the activated toxin attaches to specific receptor sites, it paralyzes and destroys the cells of the gut wall, allowing the gut contents to enter the insect's body cavity. Poisoned insects may die quickly from the activity of the toxin or may stop feeding and die within 2 or 3 days from the effects of septicemia (blood-poisoning).
- Debate on Transgenic species – Extended response.
Transgenic species are used to speed up the introduction of existing characters into a strain/breed for improvement and modification and/or developing animals specially created for use in xenografting, i.e. modify the antigenic make-up of animals so that their tissues and organs can be used in transfusions and transplants.
Bioethics addresses the impact of technology on individuals and societies. Bioethical issues include beliefs about animals and nature, and the relationship of animals with humans and the demonstrable and possible consequences of producing and using transgenic animals, including those related to animal welfare, ecology and the environment, economic and social factors, and human health.
1. Use of animals in biotechnological research causes great suffering to the animals. But most people seem to accept some animal suffering to serve the basic interest and welfare of mankind; this attitude has been termed as interest-sensitive speciesism.
2. It is felt that by using animals for the production of pharmaceutical proteins we reduce them to mere factories. This seems not to recognize that animals also are living beings which feel pleasure and pain just as we do.
3. Some people feel that animals should be regarded as equal to humans in that they have the same basic rights as human beings. However, in most societies animals are relegated to a position several steps below that of man.
4. An argument attempts to focus on integrity of species in that each biological species has a right to exist as a separate identifiable entity. But biologists do not regard a species as a fixed, water-tight entity; rather they are regarded as dynamic, constantly evolving groups.
5. Finally, the introduction of human genes into animals, and vice versa, may be seen by many as clouding the definition of "humanness". But most of the known human genes are not unique, and comparable genes do occur in animals. In addition, many retroviruses have integrated into the human genome without any recognizable devaluation of our humanness.
Reference
Book
Rhonda Caddy and Jane West, 2003, Macquarie Revision Guides, Macmillan Education, Australia
Websites
Mettler Toledo, United States Patent 6063629, US, viewed 18 May 2010, http://www.freepatentsonline.com/6063629.html
