What is phenotype?

• A. The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
• B. The array of alleles present in an organism.
• C. The complete genome sequence of an organism.
• D. The metabolic rate of an organism.

Answer: (A)

Phenotype is the observable traits of an organism—the characteristics you can see or measure, such as height, eye color, and metabolic traits—that arise from how its genes interact with the environment. In other words, the genotype provides the genetic blueprint, but the environment and gene expression determine the actual traits that appear. The array of alleles present describes the genotype, the complete genome sequence is the full genetic blueprint, and metabolic rate is just one example of a trait rather than the definition of phenotype itself.