Luria and Delbruck grew many liquid cultures of bacteria then spread a small sample of each culture on nutrient agar infused with bacteriophage in separate petri plates. They assayed the number of bacterial colonies that formed on each plate. What did the results of the Luria Delbruck fluctuation experiment indicate?
A) All bacteria are naturally resistant to infection by phage.
B) Some individuals in any bacterial population are resistant to infection by phage.
C) Exposure to phage induces some bacteria to mutate and become resistant to phage.
D) Resistance to phage in bacteria is caused by random spontaneous mutation.
E) Some phage mutated to produce large plaques with sharp edges.
D) Resistance to phage in bacteria is caused by random spontaneous mutation.
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You are given two populations of true-breeding tomato plants with two traits that sort independently. Using the multiplication rule, how many of the F2 progeny would you expect to have a dominant phenotype for both traits?
A. 9/16 B. 6/16 C. 3/16 D. 1/16
Homeotic genes generally control
a. X chromosome inactivation. b. the formation of a specific body part. c. hormone synthesis. d. dosage compensation. e. DNA methylation.
Phosphofructokinase is regulated by a number of factors, including high levels of ATP. Why is this enzyme regulated by ATP levels?
A. If ATP levels are high, this provides a mechanism to directly inhibit the Citric acid cycle, thus preventing further generation of NADH, FADH2 and ATP molecules that are not needed. B. If ATP levels are high, this provides a mechanism to directly inhibit the electron transport chain, thus preventing the formation of a proton gradient in the intermembrane space of mitochondria. C. If ATP levels are high, it is important to directly inhibit the reaction that commits the substrate to glycolysis to allow the substrate to be available for other reactions, since the cell has ample energy. D. If ATP levels are high, it is important to inhibit ATP synthase, and phosphofructokinase directly inhibits ATP synthase.
Respond to the following statements in reference to the five kinds of behavior listed below.
A. If the young of precocial (young that are relatively mature and mobile when hatched) birds (e.g., chickens or ducks) are continually shown a large moving object during the first few days of their lives, they will follow that object. This is an example of __________. B. The extreme variation in plumage observed among the males of various species of ducks is thought to be due to __________. C. A garter snake avoids dangerous or unpalatable prey. This is an example of __________. D. Instinctive responses are advantageous when the __________ consistently signals the same situation. E. Pigeons and squirrels that live in cities do not flee approaching humans due to this type of learned behavior.