wild type

The wild type is the standard, most common version of a gene or trait found in a natural population, the form scientists treat as the normal baseline. When a fruit fly has the usual red eyes rather than an unusual white pair, those red eyes are the wild type against which other forms are compared.

Geneticists use the wild type as a reference point. By comparing a mutant, which carries an altered gene, against the wild type, they can see exactly what difference the change makes. Almost every statement that a mutation “causes” some effect is implicitly a comparison to the wild-type form.

Despite the name, the wild type is not necessarily a single perfect or original sequence. In many species several common forms coexist, all reasonably regarded as wild type, and the wild type can differ from one population or place to another. It is a practical baseline, not an ideal standard of correctness.

The concept is most useful in the laboratory and in defined populations. In humans, with so much normal variation and no single “correct” genome, geneticists more often speak of common versus rare variants, or of a reference sequence, rather than of a strict wild type.