What is the term for the genetic makeup of an organism?

The term for the genetic makeup of an organism is genotype. It describes the genes or alleles an organism carries, whether across its entire genetic material or at a particular gene location.

A genotype helps produce an organism’s phenotype—the observable traits such as flower color, height, or blood type. The two concepts are related but not interchangeable: genotype refers to inherited genetic information, while phenotype reflects how that information is expressed, sometimes together with environmental influences.

In a diploid organism such as a human or a pea plant, an individual typically carries two alleles for each gene. Matching alleles produce a homozygous genotype; different alleles produce a heterozygous genotype. For example, Mendel’s pea plants could have PP, Pp, or pp genotypes, even though PP and Pp could share the same dominant phenotype.

The word genotype was coined in 1903 by Danish botanist Wilhelm Johannsen. A common mix-up is calling a chromosome or an allele the organism’s genetic makeup: chromosomes contain DNA, and alleles are alternative forms of a gene, whereas genotype describes the inherited genetic combination itself.