In Chase and Hershey’s experiments on bacteriophages, why were radioactive sulfur and phosphorus chosen as tagging elements?
a. Both isotopes have similar half-lives, so measurements would not be confounded by radioactive decay.
b. Both sulfur and phosphorus are vital to viral metabolism and are readily absorbed into bacteriophages.
c. Sulfur doesn’t occur in DNA, nor phosphorus in protein, so these molecules could be easily distinguished.
d. The radiation emitted by these isotopes is strong enough to be detected without being lethal to the cells.
c. Sulfur doesn’t occur in DNA, nor phosphorus in protein, so these molecules could be easily distinguished.
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Direct selection involves inoculating cells onto growth media on which
A. the mutant but not the parental cell type will grow. B. the mutation will be reversed. C. the nutrients necessary for mutation to occur are present. D. the mutagen is present.
If ancestral humans did not develop an opposable thumb, grasping fingers, and binocular vision, how might their history have differed?
A. They would have been less able to occupy the trees. B. They would have been unable to develop spoken language. C. They would have been less able to walk upright. D. They would have been unable to survive without changing their diet.
The type of microscope that magnifies an object up to 100 million times is a
a. compound light microscope. b. stereoscope. c. transmission electron microscope. d. scanning electron microscope. e. scanning tunneling microscope.
During forced inhalation, the __________ intercostal muscles contract, moving __________ upward
a. internal; the diaphragm b. internal; the ribs c. external; the diaphragm d. external; the ribs e. external; both the diaphragm and the ribs