Which of the following may result from improper activation of B cells by self antigens?
A. Production of autoantibodies
B. Allergic reactions
C. Anergy
D. Peripheral tolerance
E. Production of self-reactive T cells
Answer: A
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The major phagocytic cells in the body are
a. macrophages and monocytes. b. macrophages and neutrophils. c. macrophages and mast cells. d. monocytes and mast cells. e. monocytes and basophils.
How can freeze-fracture be used to determine the orientation of a protein in a membrane?
A. Freeze-fracture cuts the membrane in protein-sized components for viewing under an electron microscope. B. Freeze-fracture allows a cell to be cleaved in such a way as to preserve the embedded proteins. C. Freeze-fracture allows a cell to be cleaved in between the lipid bilayer, splitting the plasma membrane into two layers.
Which of the following statements about plant tissue culture is false?
A. Individual cells can give rise to whole plants through tissue cultures. B. Synthetic hormones can be used to selectively promote root or shoot formation. C. A callus is a mass of undifferentiated cells. D. Virus-free crop species can be propagated by culturing meristems. E. Callus tissue can only form roots, not shoots.
Describe the effects of mutating a sigma factor gene in bacteria
What will be an ideal response?