Discuss the phenomena of immunological tolerance and autoimmune disease
What will be an ideal response?
Immunological tolerance is the phenomenon that protects the body's own tissues from attack by the
immune system. Self-antigens are typically not recognized as foreign by B and T cells, and do not
induce an immune response. Those B and T cells that do react with self-antigens are destroyed during
their differentiation in the bone marrow and thymus, respectively. This occurs throughout the lifetime
of the individual. Failure of this immunological tolerance results in autoimmune disease, which is the
production of antibodies against the molecules of the body. In most cases, the effects of such anti-self
antibodies are mild. However, in about 5?10 percent of the human population, they can cause serious
problems. Autoimmune diseases include: type I diabetes (where the insulin-producing cells of the
pancreas are attacked); systemic lupus erythematosus (antibodies against blood cells and platelets, and
potentially the heart and kidneys); rheumatoid arthritis (self-attack on joints); and multiple sclerosis
(antibodies against a protein in the myelin sheaths surrounding neurons).
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Homeotic genes:
A. encode transcription factors. B. specify the identities of individual body parts or segments during development. C. are controlled by segment-polarity genes expressed earlier in development. D. are found in a wide variety of animals with bilateral symmetry, from fruit flies to vertebrates. E. All of these choices are correct.
All of the alleles in a population are referred to as ________
a. mutations b. the allele frequency c. the gene pool d. the population e. genetic equilibrium
In a clinal variation, the organisms may
a. look identical. b. not have a normal lifespan. c. never be able to mate successfully. d. vary in appearance due to adaptations to different environments. e. vary in appearance due to human interference.
Which of the following methods may help conserve water by reducing the amount used for agriculture?
A) construction f dams for irrigation needs B) reducing pesticide and fertilizer usage C) contour with no-till farming D) polyculture E) biological pest control