What could cause the lac operon to shut off after it has been activated?
A. The binding of the sugar lactose to the promoter
B. The inactivation of RNA polymerase by the addition of a modified sugar
C. The binding of the repressor to the operator after all the lactose is degraded
D. The binding of the repressor to the promoter
Ans: C. The binding of the repressor to the operator after all the lactose is degraded
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When does endospore formation commence?
A) when bacterial growth ceases due to limitation of an essential nutrient B) when the bacterium is undergoing binary fission C) when bacteria are dividing exponentially D) following bacterial death
Thick filaments are parallel bundles of ____ molecules
a. actin b. tropomyosin c. acetylcholine d. myosin e. troponin
A fish is observed as having a high and narrow tail. It is an active swimmer and appears to have a very streamlined body. What is the body type of this fish?
a. Fusiform body shape b. Depressed body shape c. Globular body shape d. Laterally compressed body shape
The ?S and ?A alleles can be distinguished on the basis of __________
A) variations in the length of their DNA restriction fragments B) variations in the length of the amino acid sequence C) different electrophoretic mobilities caused by a single amino acid substitution D) variations in the length of both the DNA restriction fragments and the amino acid sequence (both A and B) E) variations in the DNA restriction fragments and different electrophoretic mobilities of the protein products due to a single amino acid substitution. (both A and C)