Which term describes the physical expression of a gene?

The term that describes the physical expression of a gene is "phenotype." This concept encompasses the observable traits or characteristics of an organism, such as height, eye color, and leaf shape in plants, which result from the interaction of its genetic makeup (genotype) and the environment.

In genetics, the phenotype is what can be seen or measured, representing the visible manifestation of the underlying genetic information. For instance, if a plant has a genotype that includes a gene for tall growth, the phenotype would be observed as a tall plant.

Other terms in the context of genetics refer to different concepts. The genotype refers to the genetic constitution of an organism, which may include dominant and recessive alleles but does not provide a direct observation of the organism's traits. An allele is a variation of a gene that can result in different traits, while a chromosome is a structure within cells that contains DNA. Understanding these distinctions clarifies why "phenotype" is the correct designation for the visible traits driven by genetic factors.