Lethal mutations can be recovered in bacteria if they are ________.
A. active
B. conditional
C. dominant
D. None of the choices are correct.
Answer: B
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The cytoskeleton gave rise to the nuclear envelope
a. true b. false
Which of the following examples of successional processes illustrates how disturbance can lead to alternate stable states (climaxes) in the same habitat?
A) succession of carrion feeders in the African savanna B) replacement of pines by deciduous tree species in the Piedmont of North Carolina C) grazing-induced invasion of cheatgrass and its promotion of fire in western North America D) development of beech-maple forests on Lake Michigan sand dunes
Which of the following is not considered a type of structure that may sustain epigenetic effects?
a. a protein aggregate that controls the conformation of new subunits as they are synthesized b. a proteinaceous structure attached to DNA c. a chromosome rearrangement, such as an inversion d. covalent modification of DNA, such as methylation e. All of the above may sustain epigenetic effects.
In certain motile prokaryotes, dozens of different proteins comprise the motor that powers the prokaryotic flagellum. The motor has a complicated structure, and its various proteins interact to carry out its function. Based on Darwin's explanation for the existence of human eyes, how would he probably have explained the existence of such motors?
A) Because he could not have explained their existence, he would have used supernatural agents as a temporary explanation until the gap in scientific knowledge had been filled. B) Because he could not have explained their existence, he would have concluded that the human brain has not (and probably cannot) evolve the capability to solve such complex problems. C) He would have proposed that these motors were the products of aliens, and had been delivered to Earth by extraterrestrial visitors. D) Faced with such complexity, he would have given up science. E) He would have proposed that less complicated, but still functional, versions (though maybe with a different function) had existed in ancestral prokaryotes.