With respect to orthomyxoviruses, changes in antigenicity usually occur as a result of
A. frameshift mutations.
B. antigenic shift.
C. antigenic drift.
D. both antigenic drift and antigenic shift.
E. both antigenic drift and frameshift mutations.
F. both antigenic shift and frameshift mutations.
Answer: D
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Which of the following statements best describes the habitats of Acidovorax, Sphingobacterium, and Sphingomonas?
a. Habitats are limited to the upper respira-tory tract of various mammals. b. Habitats are unknown. c. Habitats are limited to the soil and water environment. d. Habitats are limited mostly to water sources.
In passive transport, the movement of a small,
nonpolar molecule across a cell membrane depends on
a. adequate amounts of ATP. b. a concentration gradient. c. adequate ATP and a concentration gradient d. the proper transport protein. e. gated channels.
Which of the following best describes the condition of a twig if the auxin produced by its apical meristem is conveyed equally down all sides?
A) It will elongate. B) It will branch near its tip. C) It will produce a flower. D) It will bend to one side.
The chromosomes are aligned midway between spindle poles during _______________.
A. anaphase B. metaphase C. interphase D. prophase E. telophase