Watson and Crick developed a model of DNA in which the two strands twist into the shape of a ________.
A. circle
B. helix
C. double pleated sheet
D. double helix
Answer: D
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Human ventilation is
(a) negative pressure inhalation. (b) positive pressure inhalation. (c) negative pressure exhalation. (d) both b and c.
Answer the following statements true (T) or false (F)
1. Most extremophiles are archaea. 2. A pathogen is a parasitic microbe. 3. Feeding antibiotics to livestock promotes human health. 4. Mitochondria originated from proteobacteria.
If you mate a donkey (2n = 62) with a horse (2n = 64) you get a mule. Mules are sterile and cannot produce gametes by meiosis because they
A. contain too few chromosomes. B. have an odd number of chromosomes. C. have an even number of chromosomes. D. contain too many chromosomes. E. lack genes that are essential for life.
The immunoglobulin known as ________ promotes the release of histamines and other agents that produce allergic symptoms.
A. IgG B. IgE C. IgM D. IgA