When Lederberg and Tatum performed their experiments on gene transfer in bacteria that lead to our understanding of conjugation, what were their controls?
A) They mixed strains A and B together.
B) They put strain A on one side of a U-shaped tube and strain B on the other, with a filter between them.
C) They found bio- met- cells.
D) They plated strain A and strain B separately onto minimal media plates to screen for spontaneous prototrophs.
E) They observed mating bridges with transmission electron microscopes.
D
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The "poles" of a cell are its
a. centrosomes. b. centromeres. c. autosomes. d. centrioles. e. automeres.
Which of the following statements about the regulation of gene expression in bacteria is false?
a. Genes can be turned on and off as environmental conditions change. b. Constitutive genes producing enzymes that are more stable are transcribed at a slower rate. c. Most gene regulation in bacteria occurs at the level of translation. d. Constitutive genes encoding proteins required in large amounts are transcribed more rapidly than genes for proteins required in smaller amounts. e. Constitutive genes with "strong" promoters bind RNA polymerase more frequently than genes with "weak" promoters
Gametophyte plants produce
A. spores. B. eggs. C. pollen. D. None of the above is correct.
In angiosperms, the male gametophyte develops within male cones.
a. true b. false