In genetics, what does the term "phenotype" refer to?

• A. The genetic makeup of an organism
• B. The observable traits of an organism
• C. The allele combination of an organism
• D. The evolutionary history of an organism

Answer: (B)

The term "phenotype" refers to the observable traits of an organism, which encompass a wide range of characteristics such as physical appearance, behavior, biochemical properties, and physiological functions. These traits result from the interaction between the organism's genetic makeup, known as the genotype, and the environment in which it exists.

The phenotype can be influenced by various factors, including environmental conditions, developmental processes, and interactions with other organisms. This understanding highlights the importance of studying phenotypes in genetics, as they provide the tangible evidence of how genotypes manifest within individuals.

In contrast, other terms provided in the options refer to different concepts in genetics. The genetic makeup, or the genotype, specifically refers to the alleles present in an organism, while the allele combination focuses solely on the variation of genes present. The evolutionary history pertains to the broader context of how species have changed over time, which is separate from individual phenotypes. Thus, the definition of phenotype is best captured by the concept of observable traits.