The persistence of the sickle-cell anemia allele in some African populations is the result of ____.
A. a high rate of mutation of the normal allele to the sickle-cell anemia allele
B. the advantage conferred by the heterozygous form when malaria is prevalent
C. nonrandom mating
D. a decline in the occurrence of malaria in Africa
E. genetic drift
Answer: B
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a. sterilize the air as it passes over the ma-terial in the cabinet. b. protect the environment from contamina-tion by biological agents by filtering the air as it is exhausted from the cabinet. c. are completely enclosed and have gloves that enable the worker to manipulate the material in the cabinet. d. are often called laminar flow hoods.
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a. autotroph b. auxotroph c. heterotroph d. chemotroph e. photoheterotroph
Protein digestion begins in the _____
a. mouth b. stomach c. small intestine d. large intestine
The most diverse of the mammals are the
a. rats. b. bats. c. dogs. d. cats. e. equines