Spontaneous mutation rates are greatly reduced by
A) exposure to ionizing radiation.
B) reverse mutations.
C) base-modifying agents.
D) DNA repair mechanisms.
E) performing the Ames test.
D
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Bartel and Szostak hypothesized that among a large pool of RNA molecules, some of them may contain the enzymatic ability to catalyze a covalent bond between nucleotides; these can be selected for in the laboratory. The chart below shows the results from their experiment. The x-axis shows the original pool and 10 pools that were derived from their tagging of RNA with specific enzymatic functions; the y-axis shows the rate of phosphoester (covalent) bond formation. Was their hypothesis supported by this experiment and why?
A. Yes, because pools 1 to 10 show a continual increase in covalent bond formation.
B. Yes, because the original pool shows some covalent bonds were formed.
C. No, because there is only a slight increase from the original pool to the first experimental pool.
D. No, because chemical selection would only increase the rate of covalent bond formation in the first few pools.
The F2 generation (the larvae measured in comparison) is shown in the graphs at the bottom of this figure. The cluster of bollworms at lower larva weights would have which genotype?
A. Rr B. Rr or rr C. rr D. RR E. Rr or RR
Which coastal region is where seawater and
freshwater mix?
a. hydrothermal vents b. coral reef c. seamounts d. coral reefs e. estuary
In many ways, a mule is a superior animal to the horse or donkey. Mules are often stronger and can jump higher than either of their parents. Why, then, are mules considered to be a "weak hybrid"?
A) They are sterile. B) They do not live as long as horses and donkeys. C) Their offspring are progressively weaker than the parents. D) They are more prone to disease than are horses and donkeys.