Sorry if this has been covered before, and I apologize for any terminology I misuse. I’m not a geneticist. I know that co-dom genes will alter the normal ball python visually depending on if its single or double? ie example, cinnamon alters the visual in one way and super cinnamon in another way, so that each instance it can be identified. Do any of the recessive genes alter a snakes visually at all if they are in the het position. Basically, I’m curious if using a recessive in a pairing does anything for that morph other than give a het opportunity in a future breeding plan. Sometimes I see a het ‘for something’ that looks just a tad different than a non-het. Coincidence?


It seems like some do a little something funky to patterns or color but like if a het pied has a “ringer” still doesn’t mean necessarily they have it you really have to prove it out to know for sure, but yeah sometimes a “normal” with double or triple het recessives doesn’t quite look normal.


Speaking as a geneticist, no, a recessive gene, in the heterozygous state, does not alter expression in any visual manner.

Unfortunately you will hear many, many people in this hobby that will claim that some hets are “visual” or have a “marker”. This is either wishful thinking or an indicator that the gene in question is actually a subtle incomplete-dominant gene. And since we are on that topic, there are no co-dominat morphs in the hobby. Co-dominance is a relationship between two genes, not a method of inheritance


So in other words a ringer on a het pied snake is just coincidence?

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Correct. There are het Pieds that do not have ringers and there are ringers that are not het Pied

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Today I Learnt.
I’m glad you’ve said this as I would have believed the opposite and gone home happy if I had bought I pied ringer, believing it to be 100% het.

What other things do you hear going around about genetics that are false or wrongly quoted?

Too numerous to count LOL

Aside from the misuse of co-dom and the belief in “visual” hets some of the others that come easily to mind are:

-The whole “hidden gene” phenomenon (there are no hidden genes)
-You can “cure” secondary phenotypes by adding more mutations (e.g., you can cure kinking/neuro/duck-billing by adding five bazillion other mutations to the combo)
-The argument of “… because ball python genetics…” as if genetic behaves differently in ball pythons than every other organism on the planet
-The belief that SuperSpider is not lethal
-The idea that things have to look similar/alike to be allelic

And I know there are others that I just cannot recall right now

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I do think it makes sense to just go with the accepted terminology as it relates to co doms. For whatever reason that got so wide spread being used that way I think it would just confuse people to start saying it right lol.

Imagine if you started listing a pastel as “het pastel.” People would have no clue what you were talking about lol

So are saying adding more genes helps weaker genes or no they do not?

Caramel for example?

So genetics are my weakness, I’ve obviously learned the co-dom terminology which is clearly incorrect. So another question other than the caramel one above is…

Banana/Coral Glow sex link stuff, I’m really disappointed with the fact that my male will only produce males. What’s the story with the genetics part of this?

It’s no totally incorrect ,it’s co Dom but really means incomplete dominance ,how do you know you defo have a male maker?

That’s a nice list and all of them are very vital.

I’m going to have to look up this hidden gene phenomenon, I’ve not heard if it.
I’m not a spider fan but I don’t disagree with people owning them, so really I can’t add any comments on them.

Also I wondered, is DNA testing a thing for snakes? Can you tell exactly what genes are present and work out it’s exact morph/heritage or does that need a huge database of sorts to start with?

Edit: are we talking hidden gene woma here?

Lmao he’s putting it on a list of myths lol not saying it’s true


Ball pythons are different from other snakes in how they pass on their genetics. To understand how, we have to think about genetics generally. Until very recently, all snakes were thought to have ZW chromosomes.

DNA. As you know, DNA dictates the appearance and physical structure of an animal. The sex chromosomes are what give male and female animals different sex organs and structures.

Humans have an XY system. Women have XX sex chromosomes, whereas men have XY chromosomes. This means that it’s the sperm rather than the egg which decides the sex of offspring.

That’s because there’s a 50% chance the man will pass on an X chromosome, or a Y chromosome. The woman will always provide an X chromosome to whatever offspring they produce.

In animals with ZW chromosomes, females are heterogametic, i.e., they are the ones with two different chromosomes (ZW). Males are homogametic (ZZ). They have two exact copies of the same chromosome.

This means that it’s the female’s egg that decides which sex the offspring will be. It was thought for half a century or more that this was the case for all snakes—but it’s not. Ball pythons, at least, are XY rather than ZW.

In humans, the X and Y chromosomes don’t tell the body much more than what sex you are. But in some animals, snakes included, their sex-determinant chromosomes can also determine their size, color, pattern and so on as well as their sex. This is crucial to how banana ball python genetics works.

This is crucial because according to a paper in Current Biology

, the banana ball python morph is in the snake’s X chromosome. It also matters because up until this discovery was made, banana ball python genetics didn’t make sense. Until recently, they were an anomaly among ball python morphs.

What’s confused breeders up until now has been this. The banana offspring of a male banana ball python whose father was also a banana will be 95% male. Female banana ball pythons can produce both male and female banana ball pythons.

But all of the banana offspring of a male banana ball python whose mother was a banana will be 95% female. Search for banana ball pythons for sale, and you’ll come across the terms ‘male maker’ and ‘female maker’ all the time—this is what that means.

This only works if the male has XY sex determinant genes, and the female has XX. To clarify further:

  • A female who has the banana ball python gene must have it in her X chromosome. Since both males and females have the X gene, she can pass it on to both male and female offspring.
  • A male who has the banana ball python gene, who inherited it from the female parent, must have the gene in their X chromosome. If the male passes on their X chromosome to their offspring, that offspring will be a female (since it will have two X chromosomes).
  • A male who has the banana ball python gene, who inherited it from the male parent, must have the gene in their Y chromosome. If the male passes on their Y chromosome to their offspring, that offspring will be a male (since it will have an X and a Y chromosome).

This wouldn’t have made sense if ball pythons had ZW genetics. If that were the case, then a male banana ball python would have equal parts male and female banana ball python offspring.

On rare occasions, genetics can bend these rules. Sometimes, part of one chromosome will detach and then attach itself to the other chromosome.

According to a paper published in Genetics

, this is known as chromosomal crossover. In the case of a male who inherited their banana gene from another male, if the banana gene crosses over to the X chromosome, their daughter could inherit it. This only happens rarely.

Why Is Breeding Banana Ball Pythons Different?

It’s different because the banana morph is a part of the X chromosome, but no other ball python morph is. There’s no such thing as a ‘male maker’ enchi, or a ‘female maker’ albino.

That’s because the genetic mutations that create these morphs aren’t within the sex chromosomes. They’re therefore passed down in equal ratios, no matter what the sex of the offspring, unlike the banana morph.

And not only that, but it’s different because other snakes are still known to have ZW chromosomes. According to the journal Evolution less genetically ‘advanced’ snakes like boas and other pythons do have ZW sex chromosomes. It’s little wonder breeders were so confused.

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Wow… I see that I have garnered a whole bunch of replies here. However, I have been tangled in meetings all afternoon and I am about to drop in to another couple hours worth so… I will hit on these replies when I can get a free minute but in all likelihood that will be tomorrow at some point.

In the meantime, please feel free to ask more questions :+1:t4:


Glad to see this got some thinking and learning and teaching going! Thanks for all the input.

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I disagree completely. Continuing to use the wrong term when you know it is wrong just because it is easy is not an excuse. Further, I would argue that a sizable section of the hobby do not even know it is wrong. When something is wrong, you work to correct it. We should be educating people, not perpetuating wrong information

I never said to call it “het Pastel”. As hobby terms, Pastel and SuperPastel are fine. But genetics is a defined science and as long as we all want to claim to understand the genetics of our animals then we should be using the terms correctly

Not. Most definitely NOT. Frequently people will try and argue that adding more morphs will fix the problem with a certain morph. This is like saying that if your car has a faulty carburetor you can fix it by smashing the tail lights.

Eaglereptiles pretty much covered it but in a bit more simple terms; The mutation for Banana/CG sits on the sex chromosomes. This, generally, means that the mutation is inherited in a fairly specific manner. In the specific case of balls, there is a slight deviation however that confuses people.

A little bit of science jargon here. In lower-level snakes, evolutionarily speaking, the sex-chromosomes follow the X/Y system and the sex-chromosomes themselves are highly isomorphic, e.g., same size and shape, (higher-level snakes use the Z/W system and the sex chromosomes are heteromorphic). Because the sex chromosomes are structurally very similar you can have material exchange between them and sometimes that material exchange involves the mutant gene. Clear as mud so far LOL?

So… The Banana/CG gene in your male sits on the Y chromosome. This means that only the offspring he produces that carry the Y chromosome (i.e., males) will inherit the mutation. But… Remember my mention of material exchange between chromosomes? That happens at about a 10% rate for the area that carries the Banana/CG gene. When that happens the mutation would switch from the Y chromosome to the X chromosome and so you would get a female carrying the mutation. So there is a possibility your male could produce a female, just at very low odds.

Make sense?

Yes, it is totally incorrect. Co-dominant and incomplete-dominant are two entirely different things. Claiming Co-dom really means inc-dom is like claiming the word “dog” really means “cat”

Yes, DNA testing is a thing for snakes but no, not at the level you are talking about.

Ben Morrill/Reptile Genetic Services offers sexing services from sheds for some species, primarily colubrids.

In theory, it is possible to build up a database like you describe however would be extremely cost-prohibitive. Sequencing in and of itself is pretty cheap these days but fully annotating a genome is no small task and then you have to comparatively analyze the genomes of every known mutation back against the wild-type genome, identify the mutation, which may be as minor as a single “letter” change out of around 1,500,000 “letters”. That takes a pretty significant amount of sequencing and a huge amount of computing power. Soft numbers… You might be able to pull it off for $500,000.

Not explicitly but that is the definite origin of the issue. Back in the dark ages, NERD had two similar looking animals that they called Woma. When they bred one to a Lesser it made your run of the mill Lesser Woma. When they bred the other to a Lesser it made a SoulSucker. And so they put forth the claim that there was some gene “hidden” in the second animal that caused the SoulSucker phenotype. The reality is that Woma and HGW are two completely different morphs. But that myth of a “hidden” gene persists… I can think of at least a half dozen other times it has been used to explain something rather than the more scientifically sound arguments people have put forth

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@t_h_wyman I get what you’re saying… but I don’t think there’s anything damaging about calling an incomplete dom a co dom. Kinda seems “get off my lawnish.”
I don’t correct someone every time they say “The definition of insanity is doing the same thing over and over and expecting different results”…even though that is incorrect.
And I don’t interrupt every time someone misuses the term “literally,” when they mean figuratively. Lol. Some things it’s ok to just let go.

I’m happy to get educated myself…but I’d choose my audience with whom I chose to get more technical. Many people aren’t going to be interested in knowing.

I thought that might be the case.
Hopefully something special can be found within snakes that will interest scientists a bit more and maybe have such a database in the future, but searching for that 1 in 1.5mil in every morph would take a whole team many years. Then again is there a “standard” wild type out there that doesn’t have some sort of genetic mutation? What snake would be our “blank” slate?

After replying I went and did some research and that’s the only conclusion I could come to myself. If these two animals are branching off completely different ways then they are not related. They obviously have a different ancestors.

What I should put was , For some reason the wrong terms are used to describe genetic heritage in the ball python context. What you know as co-dominant in ball pythons is in all actuality incomplete dominance. Vin Russo covers this topic in his book, The Complete Boa Constrictor.