Short answer
Genotype describes the DNA variant or variants present, often at a named location. Phenotype is what can be observed or measured about an organism, such as a trait or a disease manifestation. Genotype can influence phenotype, but the environment and other genes often matter too. 1 2
Genotype is inherited sequence information; phenotype is an observed outcome that may depend on genotype and environment.
On this page
At a glance
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| Question | Genotype | Phenotype |
|---|---|---|
| What it describes | DNA sequence or variant call | Observable characteristic |
| How assessed | Genetic testing or sequence analysis | Observation or measurement |
| Example | A pair of variants at one locus | Measured height or blood type |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Genotype. The genetic sequence or set of variants an organism carries, often specified at a particular locus. 1
Phenotype. An observable characteristic of an organism arising from genetic and environmental influences. 2
Key differences
A genotype is not itself a visible trait. The same genotype can produce different phenotypes under different conditions, and a similar phenotype can arise through different genetic paths. Genetic studies connect the two, but connection does not mean a one-to-one translation. 1 2
A genotype call can be made at one location without describing the person as a whole. Researchers may then ask whether that call correlates with a phenotype across many individuals. A correlation, however, can depend on other genes and conditions; it is not a one-step translation from two letters in a laboratory report to one inevitable trait. 1 2
How to tell them apart
Look at what was measured. Letters such as AA or AG at a named locus report genotype; a measured clinical or physical characteristic reports phenotype. A report can include both, but each field answers a different question. 1 2
Where they overlap
Both describe the same organism and can be causally connected. A laboratory may record a genotype to help explain an observed phenotype. 1 2
Edge cases
Phenotype includes characteristics that require tests, not only what the naked eye sees. “Genotype” can mean a single locus, a panel of loci or an entire genome depending on context. Environment can alter expression without changing the DNA sequence. 1 2
The category “observable” includes values established by clinical or laboratory measurement, not merely hair color or something visible in a photograph. Conversely, a measured trait can change over time while the inherited DNA at a tested locus stays the same. State the trait, measurement method and time when a comparison needs precision. 1 2
Why the distinction exists
The terms let researchers test how inherited variation and surroundings contribute to traits. Separating them prevents a DNA result from being mistaken for a guaranteed outcome. 1 2
Common misconceptions
A gene test does not automatically predict a person’s exact appearance or future health. Some variants have strong effects, many have small or no known effects, and circumstances can change what is observed. 1 2
Examples
Two people can carry the same genotype associated with a trait but show different measured outcomes because of nutrition, age or other genetic factors. 1 2
Sources
Sources checked October 3, 2026.
- National Human Genome Research Institute — Genotype. Definition.
- National Human Genome Research Institute — Phenotype. Definition and narration.