What is the term for the combination of alleles present in an organism?

The term that describes the combination of alleles present in an organism is "genotype." The genotype refers to the specific genetic makeup of an individual, which includes the alleles inherited from the parents. For example, an individual may be homozygous for a particular gene if it has two identical alleles or heterozygous if it carries two different alleles.

In contrast, the phenotype refers to the observable physical and physiological traits of an organism, which result from the interaction of the genotype with the environment. The term "characteristic" is more general and does not specifically pertain to genetics, while "heterozygote" refers to an organism that has two different alleles for a specific gene, representing just one possible genetic configuration. Thus, when identifying the combination of alleles in an organism, "genotype" is the most accurate term.