Which hormone in men could be manipulated to eliminate sperm production without producing problems with the maintenance of secondary sex characteristics?
A) gonadotropin-releasing hormone (GnRH)
B) testosterone
C) follicle stimulating hormone (FSH)
D) luteinizing hormone (LH)
C
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The advantage of nitrogen fixation to the host plant is
A. the ability to synthesize amino acids and proteins from the ammonia produced. B. the production of nucleotides required for nucleic acid synthesis. C. the production of antibiotics that protect the plant against pathogenic soil bacteria. D. the ability to use nitrogen gas instead of oxygen gas in cellular respiration, particularly when the soil is compacted.
Which of the following is a special binding substance that enhances immunogenicity and prolongs antigen retention at the injection site?
A. Booster B. Antibodies to toxin C. Adjuvant D. Gamma globulin E. "Trojan horse" recombinant vaccine
The accompanying figure shows the results of Jackson and Cheetham's studies on fossil and living cheilostome bryozoans. What can you infer from these diagrams?
A) Species of bryozoan have tended to persist with very little morphological change. B) Bryozoans have unusually low genetic diversity. C) Bryozoans predominantly evolve by phyletic transformation, or anagenesis. D) Bryozoans have suffered heavily from extinction events on islands. E) It is hard to define bryozoan species because of the presence of so many intermediate forms.
Class II MHC are found on
A) the skin. B) red blood cells. C) cytoplasmic membranes of nucleated cells. D) muscle cells. E) professional antigen-presenting cells.