Dark Factor in the Turquoise Parakeet
Dark Factor is an incomplete dominant mutation with three distinct, additive looks: none gives the wild-type bright green, one copy gives Dark Green, and two copies gives Olive. Unlike recessive mutations, Dark Factor is always visible — there's no such thing as a "split" bird carrying a hidden copy. It's also autosomal (not sex-linked), so cocks and hens inherit and express it identically.
What is Dark Factor?
Dark Factor is logged in this calculator's reference data as an incomplete dominant structural mutation, with a single-factor form labelled Dark Green and a double-factor form labelled Olive. Incomplete dominant mutations are the type where one copy and two copies of the mutant allele produce two different visible results, rather than one copy hiding invisibly (recessive) or one copy looking identical to two (simple dominant). Dark Factor is one of the most thoroughly documented mutations across parrot species generally — the equivalent mutation in budgerigars follows the same one-copy/two-copy additive pattern and is a textbook example of incomplete dominance in aviculture.
How it works, in plain terms
Dark Factor doesn't add or remove pigment — it thins a light-scattering structural layer in the feather, which makes the existing blue-and-yellow-built green look progressively darker and more saturated. Zero copies leaves the wild-type bright, slightly yellowish green. One copy deepens it to a rich forest-toned Dark Green. Two copies deepens it further into Olive, a muted brownish-green similar in tone to Greygreen (the Grey mutation's phenotype) but arrived at by a completely different genetic route.
Autosomal inheritance, explained
Dark Factor sits on an ordinary autosome, not the Z sex chromosome, so cocks and hens inherit it exactly the same way — there's no sex-linked complication here. Each parent passes one of their two copies at random to each offspring.
Genotype → phenotype
| Genotype | Appearance | Applies to |
|---|---|---|
| D⁺ / D⁺ | Green (wild-type, bright green) | Cocks & hens |
| D⁺ / D | Dark Green | Cocks & hens |
| D / D | Olive | Cocks & hens |
Because Dark Factor is autosomal, this single table covers both sexes — a welcome simplicity compared to the separate cock/hen tables that sex-linked mutations like Cinnamon or Opaline require.
Sources & honesty note
The inheritance type, symbol, and category for Dark Factor in Neophema Pulchella come from this calculator's own compiled reference library. The plain-language explanation of incomplete dominance and structural pigment layering above draws on well-established, cross-species psittacine genetics (the equivalent mutation is extensively documented in budgerigars); it has not been verified line-by-line against Neophema-pulchella-specific photographs. See the full references page for this project's other sources.