Free Crested Gecko Morph Calculator

How Crested Gecko Genetics Work

Lilly White is the most understood trait in crested geckos. It is an incomplete dominant — one copy produces the visible Lilly White phenotype (brightened, intensified coloration), and two copies (Super Lilly White) are lethal. Super Lilly White offspring hatch but typically die within the first week: they show breathing difficulty, motor deficits, and inability to eat. This is distinct from a recessive lethal that kills in the egg. Do not pair two Lilly White geckos unless you accept that 25% of the clutch will not survive.

Axanthic and Phantom are fully recessive traits with confirmed Mendelian ratios. Axanthic removes xanthophore (yellow and red) pigment, producing paper-white pattern on a black or brown base. Phantom is separate from Patternless — both are recessive, but at different loci. Phantom produces bicolor, buckskin, and cream phenotypes depending on background color expression. Patternless (PTL) removes pattern entirely. A gecko that looks "patternless" is not necessarily homozygous for PTL — Phantom can mimic the appearance.

Dalmatian, Pinstripe, and Hypo are all dominant traits. One copy of any of these is enough to see the phenotype. Dalmatian does not follow polygenic "more spots = more spotting genes" logic the way many breeders describe it — spot density varies by line, but the Dalmatian switch itself is a single dominant locus. Homozygous Dalmatian animals tend toward heavier expression, and pairing two Dalmatians will produce approximately 25% homozygous offspring.

Hypo combines with base color epistatically. Black base + Hypo = Lavender (not a base color — it's an interaction). Red base + Hypo = Pink. Yellow base + Hypo = C2 (Cream Squared, not "Citrus"). These are combo phenotypes, not standalone morph genes.

What Is and Is Not a Gene

Several terms widely used in the crested gecko community describe phenotypes, not genes. "Brindle" is a Tiger-to-Pinstripe ratio interaction — it is not a separate gene. "Reverse Pin" is a shadow effect visible in nearly all pinstripes. "Drippy" is what Snowflake does to Pinstripe scales — not a standalone gene. "Bicolor" is a Phantom phenotype. "Lavender" and "Pink" are epistatic interactions, not base colors.

The first confirmed allelic complex in crested geckos is Sable (SA) and Cappuccino (CAPP). These two traits sit at the same gene locus, making them alleles of each other. Crossing SA × CAPP produces a Luwak (intermediate phenotype). This was confirmed through breeding tests showing you cannot produce homozygous Sable + homozygous Cappuccino offspring from the cross — proof they share a locus.

Built by a Crested Gecko Breeder

The genetics logic behind this calculator comes from the same research database used in Geckistry, a full crested gecko breeding and genetics platform. The Geckistry Genetics Library documents every known allele, trait interaction, and combo morph with breeding notes and research citations. The full Geckistry engine handles polygenic blending with observed breeding data, phenotype name generation, and multi-trait combo morph suggestions. For breeders who want to track outcomes from their own pairings and build reliable prediction data from their specific lines, the records and genetics app from BBD includes full genetics tracking for reptile programs.

If you are also planning to check the inbreeding coefficient before this pairing, the COI calculator uses 3-generation pedigree data to compute Wright's Coefficient of Inbreeding — relevant even for reptile breeders managing genetic diversity.