What term describes a genetic characteristic that is expressed in an organism?

The correct term that describes a genetic characteristic expressed in an organism is phenotype. Phenotype refers to the observable traits or characteristics of an organism, which result from the interaction of its genotype with the environment. This includes physical appearances, developmental processes, and behaviors that are influenced by both genetic makeup and environmental factors.

In contrast, genotype refers to the specific genetic makeup of an organism, including all the alleles it possesses. Alleles are different forms of a gene that can exist at a specific locus on a chromosome. Chromosomes are structures within cells that contain DNA and carry genetic information, but they represent the organization of genetic material rather than the traits that are actually manifested in an organism. Thus, while genotype, alleles, and chromosomes are all crucial to understanding heredity and genetics, phenotype specifically relates to the actual expressed traits that can be observed.