What is the phenotype?

• A. The observable traits of an organism resulting from the interaction of genotype and environment
• B. The genetic makeup of an organism
• C. The set of proteins produced by a cell
• D. The rate of metabolic reactions in a cell

Answer: (A)

Phenotype is the observable traits of an organism—what you can see or measure about them. These traits come from the genotype, the genetic information the organism carries, and from environmental factors that influence how that information is expressed. For example, two organisms with the same genes can end up with different traits if one grows in richer soil or with more sunlight. So the phenotype reflects both genetic makeup and how the environment shapes that genetic expression.

The other options describe something different: the genetic makeup is the genotype, not the outward traits; the set of proteins produced by a cell is the proteome, a molecular description rather than a visible or measurable trait; and the rate of metabolic reactions is a biochemical property that can influence phenotype but is not itself what phenotype refers to.