Which statement accurately defines a phenotype?

• A. The genetic makeup of an organism
• B. The observable characteristics of an organism
• C. The process of gene mutation
• D. The functional roles of proteins

Answer: (B)

A phenotype refers to the observable characteristics or traits of an organism, which can include physical attributes, behaviors, and physiological functions. This definition encompasses a wide range of traits, such as height, eye color, and the presence of certain diseases, which are influenced by an organism's genetic makeup (its genotype) but also by environmental factors.

In contrast, other options do not accurately represent the concept of a phenotype. The genetic makeup of an organism is known as the genotype, which provides the potential for certain traits but does not define how they manifest. The process of gene mutation pertains to changes at the genetic level that can lead to variations in phenotype, but it does not describe what a phenotype is. Lastly, the functional roles of proteins refer to phenotypic expressions at a molecular level but do not capture the broader observable traits that phenotypes encompass. Thus, the correct statement aligns with the definition of phenotype as the observable characteristics of an organism.