The Sickle-Cell Allele Is Pleiotropic (I

question 22

Multiple Choice

The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait) . Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles such as this can help explain why

• A) new advantageous alleles do not arise on demand.
• B) evolution is limited by historical constraints.
• C) adaptations are often compromises.
• D) chance events can affect the evolutionary history of populations.

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Definitions:

NLRB

The National Labor Relations Board, an independent federal agency in the United States that enforces labor laws in relation to collective bargaining and unfair labor practices.

Strikes

Work stoppages initiated by employees as a protest against their employer, often to demand better pay, benefits, or working conditions.

Business Cycle

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Strike Activity

Actions taken by workers, typically union members, where they refuse to work in order to protest against their employer's labor practices or to push for better conditions or pay.