Which of the following statements concerning B cell receptors (BCRs) is FALSE?
A) They are formed in response to an encounter with an antigen.
B) They are complementary in shape to a specific antigenic determinant that they may or may not encounter.
C) They are bound to the surface of B lymphocytes and have two antigen-binding sites.
D) Each B lymphocyte is randomly generated with antibody variable regions that determine its BCR.
E) Scientists estimate that each person forms at least 1011 different types of B lymphocytes with distinct BCRs.
A
Bloom's Taxonomy: Comprehension
Section: Elements of Adaptive Immunity
Learning Outcome: 16.16
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Researchers pulsed rapidly dividing cultured cells with radioactive thymidinefor 30 minutes. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals At the 2-hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way:
A) Radiolabeled compounds are somewhat cytotoxic, and cell division was initially inhibited. B) The cells were arrested in a nondividing state because of the treatment and could not enter M phase until several hours after the label was removed. C) The synthesis (S) phase is lengthy, about 12 hours in most cell types, and the radioactive thymidine was not present long enough for most cells to be labeled. D) There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.
DNA sequence evidence suggests that plants, fungi, and animals arose from different lineages of unicellular protists. This suggests which of the following?
A. Protists arose before the other three kingdoms. B. Early ancestors to plants, fungi, and animals could interbreed. C. Multicellular organisms only arose once in evolutionary history. D. The animal, plant, and fungal kingdoms contain some single-celled organisms. E. All unicellular organisms are now extinct.
Which of the following do proteins and nucleic acids have in common?
A. They are both made of amino acids. B. Their structures contain sugars. C. They are hydrophobic. D. They are large polymers. E. They each consist of four basic kinds of subunits (monomers).
The function of light reactions is to
a. obtain CO2. b. make carbohydrate. c. convert light energy into a usable form of chemical energy. d. regenerate RuBP.