Leopard Gecko Genetics Basics: Het, Dominant & Recessive Explained
| Recessive | Needs two copies to show visually |
| Het | One hidden copy of a recessive trait |
| Dominant/co-dominant | Shows with just one copy |
Recessive traits
A recessive trait only shows visually if a gecko inherits two copies of the gene, one from each parent. A gecko with only one copy is 'het' for that trait — it looks Normal but can pass the gene on. Two het parents can produce visual offspring even though neither parent shows the trait.
Dominant and co-dominant traits
A dominant trait shows up visually with just one copy of the gene — every gecko carrying it will display it. Co-dominant (incomplete dominant) traits behave similarly but can look different or more intense with two copies (homozygous) than with one.
What 'possible het' means
'Possible het' (often written 66% or 50% het) reflects probability based on parentage rather than a confirmed test — it means there's a calculated chance, not a certainty, that the gecko carries the gene, since visual traits don't reveal hidden recessive genes directly.
Why this matters for buyers
If you're buying with breeding plans, genetics claims from a seller (het percentages especially) are only as reliable as their record-keeping — buying from a breeder with clear, honest lineage documentation matters more than the price tag.
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A single adult leopard gecko needs a 20-gallon long tank as an absolute minimum, with a 36x18 in (40-gallon breeder) footprint now considered the recommended standard — plus a secure lid, an under-tank heater on a thermostat, a thermal gradient, at least three hides, and a shallow water dish.
Set up in this order: substrate, then heat source wired through a thermostat, then hides and water dish, then decor — and run the whole enclosure for at least 24–48 hours to confirm stable temperatures before your gecko moves in.
Hatchlings can start in a 10-gallon tank or tub, juveniles do well in 20 gallons, and adults need a 20-gallon long as an absolute minimum — with 36x18 in (40-gallon breeder) now the widely recommended standard, not just an upgrade.
Heat a leopard gecko enclosure with an under-tank heater and/or overhead heat source (halogen or deep heat projector) wired through a thermostat — a thermostat is mandatory, not optional, and heat rocks should never be used.
Leopard geckos can survive without UVB using dietary D3 supplementation, but current husbandry guidance now recommends low-level UVB (roughly 2–6% T5) as best practice — it improves D3 synthesis, bone density, and natural behavior, and views on it have shifted significantly from older nocturnal-species advice.
Keep ambient humidity around 30–40% across most of the enclosure, with a dedicated humid hide raised to roughly 70–80% to support smooth, complete sheds.