Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because
C.
toxin is inactiveAdvatages | Disadvantages |
1. GM crops are developed for pest resistance and thus the yield increases and there is less dependence on pesticides. | 1. GM crops that show pest resistance prove harmful for pollinators and hence pollination. |
2. GM crops are developed to increase the nutritional value in the crops. | 2. GM crops can lead to severe allergies in some and may not be as good in taste as the natural crop. |
3. They can be used to develop crops which are more tolerant to abiotic stresses | 3. The pollen of GM crops is also modified and can lead to the development of resistance and growth of super-weeds. Weeds prove harmful to the environment and crops. |
4. GM crops can be developed to have antibiotic properties | The intake of GM crops having antibiotic properties may lead to antibiotic resistance in some and less efficacy of antibiotic medications. |
5. GM crops can be modified to benefit humans. | 5. The patent provided for the development of GM crops has been creating problems because the companies are benefited while the farmers are at loss. |
Example. Transgenic bacteria like E.coli which produces insulin. This bacteria is genetically manipulated by introducing two DNA sequences corresponding to A and B chains of human insulin in plasmids of E. coli to produce insulin chains. Chains A and B produced separately are extracted and combined by disulfide bonds to form human insulin.
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Treatment of ADA deficiency. 1. Gene therapy was used to correct the genetic disorder called Severe Combined Immuno Deficiency (SCID) syndrome produced by adenosine deaminase (ADA) deficiency.
2. In this, Normal ADA gene copies were produced by cloning.
3. Packed into defective retrovirus, most of the viral genes were replaced by ADA gene.
4. Lymphocytes were isolated from the patients.
5. Recombinant DNA of the recombinant retroviruses were used to infect the lymphocytes.
6. The infected cells expressing the ADA gene were injected back into the patients.
7. The normal ADA gene was then expressed in the patients and ADA deficiency is partially corrected. If the gene isolated from bonemarrous cells producing ADO is introduced into embryonic cells at early stages, it could provides permanent cure.
â² Fig. 8.4. Steps involved in gene transfer for the production of growth hormone
What are Cry proteins? Name an organism that produce it. How has man exploited this protein to his benefit?