In catabolite repression systems of some Gram-positive bacteria, such as Bacillus subtilis, transcription of catabolic operons is regulated by CcpaA (catabolite control protein A) rather than cAMP. Propose a hypothesis to explain the preferential use of glucose in the presence of a second sugar such as sucrose by Bacillus subtilis.
A. CcpaA acts as an inducer of sucrose operon genes in Bacillus subtilis when glucose, but not lactose, is present.
B. CcpaA acts as a repressor of sucrose operon genes in Bacillus subtilis when both sugars are present.
C. CcpaA acts as an inducer of sucrose operon genes in Bacillus subtilis when both sugars are present.
D. CcpaA acts as a repressor of sucrose operon genes in Bacillus subtilis when lactose, but not glucose, is present.
Answer: B
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Select the statements that provide direct biogeographical evidence for evolutionary theory. Check all that apply.
_____ Unrelated organisms from similar habitats exhibit similar characters. _____ Terrestrial mammals are not found naturally on any island greater than 300 miles from a mainland. _____ Organisms on islands are most similar to organisms on the nearby mainland, even when habitats on the mainland and island are quite different. _____ Invasive rats have colonized more than 80% of the world's islands.
During times of intensive flying, bumblebees use anaerobic respiration to convert glucose to
__________.
a. lactic acid b. carbon dioxide c. acetyl CoA d. oxygen
Many gastropods have external shells composed of:
a. two valves. b. eight overlapping valves. c. a series of internal chambers. d. one valve. e. chitin.
What did Charles Darwin propose after observing the 11-inch-long nectaries of the Angraecum sesquipedale orchid in Madagascar?
A. that the orchid was an evolutionary dead end and could no longer reproduce B. the existence of a pollinator moth with a proboscis of 10–11 inches C. the presence of very small bees that can fit into a long nectar tube D. that the orchid must reproduce asexually E. that the orchid was a self-pollinator and required no assistance from an organism