What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?
A) The two phenotypes are about equally adaptive under laboratory conditions.
B) The genotype AA is lethal.
C) There has been a high rate of mutation of allele A to allele a.
D) There has been sexual selection favoring allele a.
A
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The starch production center within many algal cells is the
(a) nucleus. (b) cytoplasm. (c) stipe. (d) pyrenoid.
According to Stern's experiment described in Figure 6.17, which one of the following enzymes was shown to form an intermediate complex with its substrate(s)?
A. -galactosidase B. pepsin C. DNA polymerase D. lysozyme E. catalase
A scientist is examining motile protozoa. He wishes to determine their direction of movement. Which of the following microscopic techniques is least likely to be used to view these cells?
A) light microscopy B) electron microscopy C) differential interference contrast microscopy D) fluorescence microscopy E) phase-contrast microscopy
Which of the following statements about generalized transduction is false?
A. Two recombination events are necessary to integrate the transferred DNA during generalized transduction. B. Generalized transduction always involves lytic phage. C. Genes that are close together on the bacterial chromosome will have a relatively large cotransduction frequency. D. "Head full" packaging always places only phage DNA into the phage head during phage packaging in generalized transduction. E. Generalized transduction can be used to map bacterial genes.