Cell motility is an important identifying characteristic in laboratories. What is the best way to determine whether a bacterial strain is motile?
A) Do a simple stain and observe the organisms under phase-contrast microscopy.
B) Do a Gram stain and observe the organisms under bright-field microscopy.
C) Stab an inoculum into a tube of semisolid medium.
D) Inoculate a liquid culture with the organism.
Ans: C) Stab an inoculum into a tube of semisolid medium.
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When an allele can produce a range of phenotypes, its expression is said to be
a. clearly established. b. variable. c. codominant. d. incompletely dominant. e. incompletely penetrant.
In a typical angiosperm, what is the sequence of structures encountered by the tip of a growing pollen tube on its way to the egg?
1. micropyle 2. style 3. ovary 4. stigma A) 4 ?? 2 ? 3 ? 1 B) 4 ? 3 ? 2 ? 1 C) 1 ? 3 ? 4 ? 2 D) 3 ? 2 ? 4 ? 1
Which microscope is the most widely used to show stained cells against a bright background?
A. electron B. dark-field C. fluorescence D. bright-field E. phase-contrast
You spray your kitchen with an insecticide to kill the cockroaches. A few survive and reproduce, producing a large healthy population in a few generations that all have similar genetic backgrounds. This is an example ofÂ
A. genetic drift. B. assortative mating. C. migration. D. bottleneck effect. E. mutation.