Understanding Allelic Genes in Ball Pythons!

Guest Contributor: Warwick Von Hagen of Strictly Snakes / Edited by Justin Kobylka

Justin’s note: I’m pleased to offer a guest contributed piece here on BSJ. If you found it helpful and want to see more, comment below!

Those of you, who have recently discovered the fast growing world of Ball Pythons, have probably come across the concept of alleic genes. More than likely you are probably scratching your head and asking what ever could this be?

In this article we are going to refer to allelic genes as ALS or Acts Like Super. Lets first cover the basics of Genetics 101 before we get into understanding the ALS. I’m also including a list at the end of Ball Python mutations that fit into this unique concept.

We have to start with a basic genetics overview, let us looking at the breeding of the pastel gene (this gene is incomplete dominate. We refer to it incorrectly as “Codom” in the reptile community). Bear in mind that your actual results will vary per breeding:


Super Pastel

Pastel X Normal will result in the following offspring
50% Pastel
50% Normal


Pastel X Pastel will result in the following offspring
25% Super Pastel

50% Pastel
25% Normal

Super Pastel X Normal will result in the following offspring
100% Pastel

Now we can move on to the next step. In this step we will cross 2 different mutations together. The breeding’s we will be looking at is the Pastel x Spider pairing:


Enchi Bumblebee YB

From the pairing mentioned above, the resulting offspring will be:
25% Bumble Bee
25% Pastel
25% Spider
25% Normal


Now, if we took that Bumble bee and bred it to a normal, we will hatch the following:
25% Bumble Bee
25% Pastel
25% Spider
25% Normal

As you can see, by breeding a Pastel x Spider OR breeding a Bumble bee x Normal, the exact same result ratios apply.

If you understand the basic genetic concepts above, let us looking at the ALS. The official name for ALS is in fact Compound Heterozygous. It refers to when two Alleles (alternate forms or varieties of a gene) meet at the same Locus (the location of allelic genes on the chromosome) creating a genetic mutation composed of two different genetic ingredients.

The slang term “Acts Like Super” was derived to define two distinct genes that pair at the same locus but have different but compatible alleles. The resulting combo generally has a dramatic visual expression. When bred to a normal all resulting babies are gene carriers of this combination. 50% of all offspring receiving a single copy of a gene. This combination cannot reproduce itself when bred to a normal since it occurs at the same locus and can only reproduce the “ingredients” in the parent animal.

Highway Piebalds – (Highway is an ALS combo)

Since this is a paired gene mutation you must understand the difference between an ALS and a standard double mutation. With a combo such as a Pastel x Spider (as discussed earlier) we are looking at two distinct Locus sites to define the presence of these genes. Pastel does NOT share the same Locus as Spider and we are seeing the overlapping of two expressed genes on the same snake. With ALS we are seeing two genes on the SAME locus and the resulting pair of genes makes the visual combo. This is basically the same type of behavior we see with “super form” genetics.


So, what does this mean with regards to breeding?? Well, let us look at a few pairings; the two “base ingredients” we will use is that of Yellow Belly and Spector.

Separately, the Yellow belly and Spector genes are visually different from each other and make different combos, but when combined together, the work as a Compound Heterozygous animal or ALS.


Super Stripe (Yellowbelly Specter)

So, let’s start by pairing Yellow belly x Spector, the resulting pairing will produce the following offspring:
25% Super Stripe (this is the animal you want to produce, this is the ALS animal)
25% Spector
25% Yellow Belly
25% Normal


But when breed a Super Stripe x Normal, no Superstripes AND no Normals are produced.
50% Yellow Belly
50% Spector

As with all the genetics, it can be hard to initially wrap your mind around these concepts. But as you start dealing with these unique genes more, it will become easier to understand.

Now that you’re an ALS gene superstar, let’s check out the list of commonly known allelic genes in Ball Pythons.

Incomplete Dominate ALS genes

Pastel Highway

Yellow Belly Complex:



Vanilla Cream (Vanilla Fire)

Fire/ Black Eyed Lucy Complex: (some of these genes may be the same, others have small to large variation)



Phantom / Super Phantom (img credit ukn)

Blue Eyed Leucistic Complex:
Russo het Leucistic



Blackhead Spider – this allelic combo nearly wipes out traces of both genes. photo: Michael Freedman


Cinny / Black Pastel Complex:

Black Pastel
Het Red Axanthic
Brown Back
Green Pastel


Blackhead & Spider are allelic. The combination of these two genes nearly wipes out visual traces of either of them. A very surprising result.

Recessive ALS Genes: These are visually different recessives, but when combined, they still create a homozygous animal.


Albino & Candy Albino (aka Candino) photo: Matt Jablonski

Candy/Toffee Complex:


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