The combination of its alleles determines a trait of an organism. Alleles are alternative forms of a gene that can have different effects on the organism's phenotype, or observable characteristics. The combination of alleles inherited from both parents determines which traits are expressed in the organism. The phenotype is the result of how these alleles interact and express themselves in the organism's physical appearance or behavior. The number of copies of the gene and the number of dominant alleles may influence the expression of a trait, but the actual determination of the trait is based on the combination of alleles.
