Which of the following terms best describes a genetic characteristic that is not expressed in the phenotype?

A genetic characteristic that is not expressed in the phenotype is described as recessive. This term refers to alleles that do not manifest in the observable traits when a dominant allele is present. For an organism to exhibit a recessive trait, it must inherit two recessive alleles, one from each parent. If only one dominant allele is present, it will mask the effect of the recessive allele, thus preventing it from being expressed in the phenotype.

In contrast, a dominant allele is one that will express its trait even when paired with a recessive allele. Co-dominance involves the expression of both alleles in a heterozygous organism, leading to a phenotype that shows characteristics of both alleles simultaneously. Autosomal traits pertain to genes located on non-sex chromosomes and do not specifically refer to expression levels of dominant or recessive alleles. Thus, the term that accurately describes a genetic characteristic not expressed in the phenotype is recessive.