# Royal Python Genetics For Beginners



## Pyro

I took the time and effort to write all this myself, as I have now come to learn the basics of genetics and royal python breeding. I could not find one single guide out there easily which contained every basic I needed to know, so I decided to create one. This is all written in my own words, even though I learned the information from other sources online, so I hope you other beginners find it useful.​ 

*Royal Pythons - Breeding & Genetics*​ 

Every royal python has genes in its DNA which give it certain traits. Traits are things that will distinguish it from other snakes, such as colours and patterns. When breeding royal pythons it is important to select parents with the correct genes to give the offspring the desired traits. For example, if you wanted albino offspring it is no good using two normal parents, but it is also more than that. Genes are either recessive, dominant or co-dominant, and depending on which type they are will depend on the parental pairing required to produce the correct traits in offspring. First, lets look at what those terms mean.

*Recessive* genes are dominated by dominant genes, meaning if both a recessive and dominant gene are present the dominant gene will be visual in the snake rather than the recessive gene. Therefore for a recessive trait to be visual in a snake, both parents must carry the recessive gene. 
For example, the albino gene is recessive, so if a normal royal python and albino royal python mated, none of their offspring would be visually albino as none of them would inherit two albino genes. Those that inherited a single albino gene would be ‘het albino’ (meaning they are heterozygous and carry the gene just like one of their parents did), whilst the others would just be normal royal pythons.

*Dominant* genes dominate recessive genes, meaning if both a dominant and recessive gene are present the dominant gene will be visual in the snake rather than the recessive gene. Therefore for a dominant trait to be visual in a snake, only one parent needs to carry that dominant gene.
For example, the spider gene is dominant, so if a normal royal python and a spider royal python mated, some of the offspring would inherit the spider gene and be visually spider. Those that inherited a normal gene from both parents would be normal, and those that inherited one normal gene and the spider gene would be spider, so there is no possibility for het spider royal pythons.

*Co-Dominant* genes are dominant genes but are heterozygous instead of homozygous. This means that although only one parent needs the gene for it to be visual in the snake, just like a dominant gene, there is also another possibility. If both parents carry the co-dominant gene the visual effect on the offspring will be distinctly more obvious, and a ’super’ form of the trait is present. 
For example, the pastel gene is co-dominant, meaning if a normal royal python and a pastel royal python mated, those offspring which inherited the pastel gene would be visually pastel and those that inherited normal genes would be normal. However, if two pastel royal pythons were to mate, those offspring which inherited a pastel gene from both parents would be visual for the super-pastel trait.

So to summarise this section, heterozygous (het) is when the snake only has one of a particular gene, and homozygous is when it has two of that gene. When a snake is het for a recessive gene, the trait is not visual, but when the snake has two of that gene the trait becomes visual. In a snake with a dominant gene, it does not matter if it is heterozygous or homozygous as it only takes one of the gene for the trait to become visual, so any snake with that dominant gene will visually show it. Finally, snakes which are heterozygous for a co-dominant gene (so only have the one gene) will still show it visually just like a dominant gene, however if homozygous for the trait (has two of the gene) it will be visually super for that trait.



Here are some charts showing what the offspring would be of two parent snakes which are carrying different genes. As you can see, depending on the genes and their type, the amount of a particular trait in the offspring can vary.

*Chart 1.*
First up, here is the chart for two normal royal pythons and their offspring. The left column represents the genes from the mother and the top row those from the father. In this case two parents with the normal trait (AA) pass on one gene (A) each, meaning the offspring have one normal gene (A) from the father and one normal gene (A) from the mother, resulting in AA (normal offspring). 100% of the offspring would be normal royal pythons, a visual dominant trait.

*Chart 2.*
Next up, here is the chart for a female normal royal python and a male spider royal python and their offspring. In this case, the mother passes on two normal genes (AA) while the father passes a normal and a spider gene (AS). As you can see, half of the offspring would receive both a normal and a normal gene, making them visually normal royal pythons. The other half would receive a normal and a spider gene, making them visually spider royal pythons. So 50% of the offspring would be normal and 50% of the offspring would be spider.

*Chart 3.*
Next up, here is a chart showing that to get visual albino offspring you can breed a het albino mother and a het albino father. The albino gene is represented by an a, it is a lower case letter to show that it is recessive. As you can see, one in four offspring would receive two normal genes, one from each parent, and be visually normal royal pythons. Two in four would inherit one normal and one albino gene, and as albino is recessive the normal gene would be visual, making them het albino like their parents. Only one in four would inherit two albino genes, one from each parent, and be a visual albino royal python. As three of the four would look normal, and two of these would be het albino, the three are considered to be 66% het albino. This means if you took one at random, there is a 66% chance it would be one of the two which inherited the albino gene, just simple mathematics really.

*Chart 4.* 
Next up, here is a chart showing a normal female royal python breeding with an albino male royal python. The female has two normal genes (AA) and the father, being visually albino, has two albino genes (aa). As you can see, because every single offspring would inherit both the normal and albino gene, and albino is a recessive trait, all the offspring would be het albino. This is why you can not get visual albino offspring from breeding a normal to an albino, both parents must carry the recessive gene. Since every single offspring would look normal but carry the albino gene, they are all considered to be 100% het albino. Every single one of them will carry the albino gene.

*Chart 5.*
Finally, here is a chart showing a co-dominant gene. In this case two pastel royal pythons have been bred together and we take a look at the offspring they would produce. Both mother and father are het for pastel (AP), and as it is co-dominant they are visually pastel. As you can see, one in four of the offspring would inherit two normal genes and would be a normal royal python. Two in four would inherit the pastel gene alongside a normal gene and be het pastel. Since this is a co-dominant gene, they would (unlike the recessive gene) be visually pastel even though only het for the trait. One in four would inherit two co-dominant pastel genes, and the result would be a super-pastel royal python.


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## Pyro

*Part 2*​ 

As I intend to breed for both the Spider and Pastel traits, I can expect to have five kinds of offspring. These are normal, spider, pastel, super-pastel and bumblebee royal pythons. The bumblebee royal python carries genes for both the spider and pastel traits and expresses them both visually, however it is rare for one to be born even amongst larger litters. Here are some more examples of the offspring I could hope to produce from more advanced breeding of pastel and spider genes.

Let’s assume I start my breeding project with two normal female royal pythons, a male spider royal python and a male pastel royal python. All are of breeding age and so I put each male with a normal female. If the snakes lock, meaning the male is impregnating the female, she will have eggs develop inside her. After ovulation (the laying of the eggs) the eggs will be incubated for around 60 days before they hatch. But what morphs will emerge from the eggs? Let us use charts again to explain.


First, the normal female and spider male:
*Chart 6.*
50% of the offspring are normal royal pythons.
50% of the offspring are spider royal pythons.

Next, the normal female and pastel male:
*Chart 7.*
50% of the offspring are normal royal pythons.
50% of the offspring are pastel royal pythons.










Now let us assume I sell on the unwanted offspring but keep hold of a few snakes which I will use for breeding once they have matured. In the next possible breeding season, when all the offspring from the above charts are of breeding age, I pair them up as follows:

First, a pastel female and a pastel male:
*Chart 8.*
25% of the offspring are normal royal pythons.
50% of the offspring are pastel royal pythons
25% of the offspring are super-pastel royal pythons

Next, a pastel female and a spider male:
*Chart 9.*
25% of the offspring are normal royal pythons.
25% of the offspring are pastel royal pythons.
25% of the offspring are spider royal pythons.
25% of the offspring are bumblebee royal pythons (PS), they carry both the pastel and spider genes.











If I am lucky, I will have at least one of each of the super-pastel and bumblebee royal pythons, which I can either sell or keep for my own collection, or for future breeding. All the unwanted snakes produced would be sold on as pets and so none of the offspring would be wasted whilst breeding out the bumblebee or super-pastel traits. All the snakes would be worth breeding, these two traits would just be the icing on the cake.


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## Ssthisto

Pyro said:


> *Recessive* genes are dominated by dominant genes, meaning if both a recessive and dominant gene are present the dominant gene will be visual in the snake rather than the recessive gene. Therefore for a recessive trait to be visual in a snake, both parents must carry the recessive gene.


Keep in mind this is on the same gene pair - matching a Pied (recessive) to an Albino (recessive) will not display EITHER recessive morph - because the albino carries dominant "Not Pied" and the Pied carries dominant "Not Albino".




> *Dominant* genes dominate recessive genes ...





> Those that inherited a normal gene from both parents would be normal, and those that inherited one normal gene and the spider gene would be spider, so there is no possibility for het spider royal pythons.


This is not technically accurate. An animal with one spider gene and one normal gene* is* "het for Spider" - this just happens to be visible BECAUSE Spider is dominant. Heterozygous ONLY means "the two copies of the gene are different".




> Co-Dominant genes are dominant genes but are heterozygous instead of homozygous.


This is completely wrong, I'm afraid.

Codominant traits have three different visual phenotypes - a non-carrier is a normal. A heterozygous carrier with only one copy of the mutant trait looks different to a normal AND looks different to a homozygous carrier with two copies of the mutant trait. The Mojave gene is codominant to normal; it just looks different if you've got a homozygous animal compared to a heterozygous one.

A Dominant gene by definition looks EXACTLY the same whether it is heterozygous OR homozygous.


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## Blackecho

http://www.reptileforums.co.uk/genetics/211114-genetics.html

This is a thread I made a while back, it isn't perfect, but might fill in a few of your gaps.


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## Pyro

Thanks for clearing up the co-dominant part, and thanks Blackecho that guide is also really good. So what do you think of my guide apart from the mistakes, is it easy to understand?


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## paulh

Hi Pyro, 

Looks like you are starting to get a handle on genetics. Here are a few tips:

1. Dominant, recessive, and codominant ALWAYS imply a comparison between TWO genes. The comparison is implicit or explicit. If I write "The albino mutant gene is recessive to the normal gene", then the comparison is explicitly to the normal gene. If I write "The albino mutant gene is a recessive", then the comparison is ALWAYS implicitly to the normal gene.

2. Have you gotten into multiple alleles yet? Some of those blanket statements do not apply when there are multiple alleles.

3. The pro geneticists use a lower case letter to symbolize recessive mutants, an upper case letter for dominant and codominant mutants, and a plus character (either alone or as a superscript) for the normal gene. So if a is for albino (a recessive), then + or a with + as a superscript is for the normal gene. If P is for pastel, then + or P with + as a superscript is for the normal gene.

4. Chart 9 is wrong because you are using one gene pair instead of two. The spider has two normal genes at the pastel locus and a spider mutant gene paired with a normal gene at the spider locus. The female has a pastel and a normal gene at the pastel locus and two normal genes at the spider locus.

5. Short sentences are easier to understand than long, involved sentences. Examples:
All gene pairs are either homozygous or heterozygous.
The two genes in a homozygous gene pair are the same.
The two genes in a heterozygous gene pair are not the same. They are different.


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## guardian

:gasp:i believe that was my head that just exploded!!!!!!:gasp:


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## emmabee

not quite sure i understand this yet! if i put a spider male to my normal i would have visual spiders in the first clutch? will the colouration on the female make a difference? one of my normals is very yellow whilst the other is choclatey so would this make a difference when selecting a dominant gene for use? if the visual bit is right what else is a dominant gene?:blush:


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## Ssthisto

Yes, if you put your Spider male (who is almost certainly heterozygous for the probably-dominant Spider gene) to your Normal female, you have a 50% chance (assuming heterozygous) of getting spider offspring.

Yes, the colouration on the female might make a difference - that gets into "polygenic" traits, where there are lots of little individual effects of various genes that might influence the overall appearance, but where it's much harder to pick out single, simple traits. So a very yellow female might make spiders that are more yellow and brighter than the dark female's spider offspring, even if the spider gene came from the same male in both cases.


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## Marco 1986

This is amazing... I'm looking at what to breed my het albino with... This has helped a lot... Thank you... Marco


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## alan1

i think your diagrams would be much easier to follow if the Normal gene was expressed as .* N*

selecting one of your punnetts as an example, this would show a 'pastel x spider' projected outcome as

......*N* ... *P*
*N*... N... .P
*S*... S... PS


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## Blackecho

You're about 2 years late Al


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## alan1

Blackecho said:


> You're about 2 years late Al


closer than usual then! still applies tho : victory:
you would have thought the section mod would've spotted it too!


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## Ssthisto

alan1 said:


> closer than usual then! still applies tho : victory:
> you would have thought the section mod would've spotted it too!


Section Mod replied to the person who'd posted recently, instead of original poster


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## alan1

yep, same as! - these old threads appear to be making quite a comeback of late!


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## Marco 1986

alan1 said:


> yep, same as! - these old threads appear to be making quite a comeback of late!


That's only because noobs like myself are trying to educate themselves...:lol2: Guess there is no harm in that though...


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## paulh

alan1 said:


> i think your diagrams would be much easier to follow if the Normal gene was expressed as .* N*
> 
> selecting one of your punnetts as an example, this would show a 'pastel x spider' projected outcome as
> 
> ......*N* ... *P*
> *N*... N... .P
> *S*... S... PS


I find this Punnett square as unsatisfactory as the original.

Reasons:
1. Symbols are not explicitly defined for both squares.
2. Both squares seem to involve one locus with three alleles. In reality, the problem involves two loci, each of which has two alleles.


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## eeji

spider x pastel (assuming the spider is het) would be written as:










resulting in 25% normal (++++), 25% spider (+++S), 25% pastel (+P++), 25% bumblebee (+P+S)


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