New to morphs? Start here

A morph is a reptile whose colour or pattern differs from the wild type because of one or more known genes. Every animal carries two copies of each gene, one from each parent, and passes exactly one copy to each offspring. This planner does that bookkeeping for you: tell it which genes each parent carries, and it works out every combination the babies could inherit and how likely each one is. It is the same Punnett square you may remember from school, just with more squares.

The result is a list of possible outcomes with a percentage next to each. A pairing with a 25% chance of a given morph does not mean one in four eggs will be that morph. It means each egg, independently, has a one-in-four chance. Small clutches can and do miss.

How to use it

1. Pick the speciesBall pythons, crested geckos and leopard geckos have different gene lists.
2. Add the sire's genesChoose each gene the male carries and whether he shows it (visual) or only carries one copy (het). A normal animal with no known genes needs nothing added.
3. Add the dam's genesSame again for the female.
4. CalculateOutcomes are listed by what the baby would look like first, then the hidden genes it would carry. Percentages are per egg.

The three kinds of gene

Recessive

Needs two copies to show. One copy is a "het" (heterozygous): the animal looks normal but can pass the gene on. Albino, piebald and clown in ball pythons, and most leopard gecko albinos, work this way. Het × het gives a one-in-four chance per egg of a visual.

Incomplete dominant (co-dominant)

One copy shows a visible change, two copies show a stronger or different "super" form. Pastel, mojave, lesser and most of the popular ball python genes are this type. Pastel × pastel gives a one-in-four chance of a super pastel.

Dominant

One copy shows the full effect and two copies look the same. Spider and pinstripe in ball pythons are the usual examples. You cannot tell a single-copy animal from a double-copy one by looking.

Visual vs. het

"Visual" means the trait is showing. "Het" means the animal carries one recessive copy you cannot see. "Possible het" (often written 66% or 50% het) means the parents make it possible but the animal has not been proven by breeding.

Super

Two copies of an incomplete dominant gene. Super pastel, super mojave (blue-eyed leucistic) and so on.

Combos

Morphs stack. A pastel that also carries clown is a "pastel het clown". The planner handles any number of genes at once, which is where the square gets too big to do by hand.

What it cannot tell you

Line-bred and polygenic traits such as "high yellow" or "reduced pattern" are selected over generations and have no simple odds. Some gene pairs are known to be allelic (they sit at the same spot and behave differently together) and a few combinations carry health concerns. The planner reports Mendelian odds only. Breed for health and temperament first, and ask a vet or an experienced breeder before pairing anything you are unsure about.