#snake genetics

[fractiousrvt]

Just had a guy try to condesplain corn snake motley and stripe to me. This guy specializes in motleys as a breeder, too. Unfortunately for him... he didn't read the thread and missed a key fact that resulted in him looking absolutely fucking stupid.

To summarize/explain:

OP relays that mom snake was purchased as a tessera. 16 eggs hatched, no tesseras but one stripe and 2 motleys are present. Meaning 13 babies were normal patterned (important).

A picture of mom was provided, showing that she is visually a motley. Because she produced a striped baby, that means genetically she is a motley-stripe (motley and stripe share the same spot in the genome. They are allelic to each other.) In a genetic motley-stripe the motley gene completely masks the stripe gene and the animal will look like a motley. The stripe gene has no effect on the motley pattern at all.

Because normal babies were produced, we know that the dad is not a motley or a stripe because otherwise every baby in the clutch would be a visual motley or stripe. Visual motley to visual motley, visual motley to stripe, and stripe to stripe cannot, genetically, produce offspring with a normal pattern (barring extremely rare genetic fuckery. We're keeping things neat here)

Because a stripe baby was produced, we know the dad must be carrying *one* copy of the stripe gene. As he *only* has a stripe gene to offer to his offspring, the motley patterned babies are actually genetic motley-stripes. And all the normal patterned babies in this current clutch are either het motley OR stripe but NOT both, thanks to mom.

I informed OP of this in a similar fashion and said that if paired to a stripe the dad will only be able to produce normal patterned and striped babies.

Then comes in

Mr. Motley

"If the dad is motley/stripe paired with a stripe he would still produce motleys and stripes..Motley is dominant to stripe in the gene pool..Matter fact if he bred the stripe and carried no stripe he would produce all motley babies het stripe..(motley/stripes) ..The motley babies do seem to come out with a lot of striping.."

to which I responded:

"The dad isn't a motley. Only 2 motleys and the one stripe were produced.

to quote OP: "only 3 aren’t the wild-type pattern haha"..."

Don't fucking try to mansplain genetics to me that I relayed correctly when you can't be arsed to read the discussion actually happening.

[omg-snakes]

Hi I am about 90% sure I'm asking the right snek tumblr but I follow like. fifty of you. Do you know what X% PH means when it's about morphs? Like I'll see something like idk 50% PH albino and what does that MEAN I've tried to look it up but have found nothing, possibly because I'm searching the wrong terms but who knows.

Anyway. Hope you have a lovely day :)

Hey friend!

PH means "possibly heterozygous," and the percentage is about how possible the heterozygous-ness is.

This comes up when you have one or both parent snakes who are known to be heterozygous for a recessive trait, but it's not certain whether or not their offspring are het since it's not visible. This isn't an arbitrary number nor a guarantee of genetics, it's just a statistical probability that the snake is carrying that gene.

For example, let's say you are breeding two wild-type corn snakes and one is het for the recessive Amelanistic gene. The babies will have a 50/50 chance of inheriting the Amel gene, but they would also be het since they can only get one copy of the trait from the one parent who carries it. Since you can't see a heterozygous recessive trait, all of the babies would be listed as 50% possibly heterozygous for Amelanism, or 50% PH Amel.

If both parents are het for Amel and neither are homozygous, statistically about 1/4 of the babies would be homozygous visual Amel, 2/4 would be heterozygous Amel wild-types, and 1/4 would be of the babies would be wild-types with no heterozygous traits at all. Percentage-wise, the wild-type babies would be 66.667% PH Amel.

Of course, nature doesn't exactly adhere to statistics, so any time you see "PH" consider it a possible bonus or advisement, but not a guarantee of genetics.

I hope that helps!

[edgysaintjust]

Found this baby baby Fouché

[oriandico]

Blah I am researching totally-hypothetical-possible-future-pets to keep my mind of The Impending Reality© and I tell ya: trying to get beyond the "oh wow that animal looks stunning" and into the "why does this mystic potion look so much different from that mystic potion" and past "this cinnamon, normal, lesser and yellowbelly all look the same to me and I will feel kinda like a moron saying that because obv the cinnamon is more cinnamon and the lesser looks kinda like it is about to shed but they seriously all still look pretty normal to me you guys aren't just messing with me are you?" point in ball python genetics is not super easy. It really doesn't help that so many breeders insist on using their own designer names for combos. Or calling the same gene two different things. Or that some morphs have issues that literally nobody talks about outside of Tumblr. Yeah. So I know I like the freckling some bananas get. I know I like the black/yellow combos some GHI(?) get? Maybe? I might not be thinking of the right gene? I love the colors of mojave but I am not a huge fan of the wild-type pattern. I know I love cute headstamps. I know I am totally lost. I do not know what morph I would want to get. Anyway; if I choose at some point in the future to get a ball python I am trying to hone in on the gene or family of genes I really enjoy and what I would be looking for, and right now it just feels like "oh yeah throw any 4 genes together and sell your kidney for the animal and you will be happy" so I am gladly taking suggestions on A) cool BP morphs B) tips on what genes do what -> what is a mystic potion gene gonna do to a combo vs a lesser vs a fire vs a whatever. (There seem to be color scheme genes, patterny genes, and then 'whelp I guess that one is just magic' genes which confuse me the most) Also: BP people have very different personalities compared to colubrid people. Just an observation.

[omg-snakes]

Could you explain to me the diffrence between the tessera, terrazzo, and stripe morphs? They all kinda look the same to me. I love your blog, all of your babies are adorable and the new babies are just so tiny!

Hey friend! 

First off, thank you so much for your kind words. :) I’m very happy about this hatching season and very excited to share all of these new faces with everyone!

Second, your very excellent question has a very simple answer with a somewhat less simple elaboration.

Answer: They’re different genes that coincidentally look similar. Tessera is dominant, Terrazzo and Stripe are recessive. Visually, Tessera usually results in very bold patterning that goes from head to tail, while Terrazzo tends to fade out towards the tail end of the snake, and Stripe is often somewhere in the middle between bold and faded.

More Answer: (under a cut because verbosity reasons)

For the sake of those who might not be as familiar with genetics, here’s a super quick, mega oversimplified crash course! Snakes, like humans, have two sets of chromosomes that provide the genetic code for their color, pattern, internal organ structure, skeletal structure, and so on. They receive one set from each parent. Each chromosome contains many genes, and each gene sits at a specific spot on the chromosome called a locus (latin for “place”). This means that the gene that determines whether or not a corn snake is amelanistic will be at the same locus in every corn snake. Think of a locus like coordinates on a map!

When we write out corn snake genetics we use a simple one or two letter abbreviation with a superscript letter or plus sign to indicate whether the gene is in the “on” or “off” position. 

Let’s look at recessive traits first. A recessive trait requires two copies of the gene in an “on” position to be expressed, otherwise the gene will default to the “normal” wild type expression. A prime example is the Amel gene, which eliminates all melanin (black pigment) on a corn snake and results in yellow, red, and white snakes with pink eyes.

An Amel corn snake’s genes would be represented like this:  aaaa    Here both copies of the Amel gene are “on” and the snake is considered homozygous (homo = same) for Amel and will appear amelanistic.

If the snake is a wild type (normal) with no amelanistic traits, that would be represented like this, with plus signs:  a+a+     In this example, the Amel gene on both chromosomes is “off” and the snake is homozygous for wild type, and they’ll have melanin like the majority of corn snakes found in their native range.

So if the snake carries one copy of the Amel gene that’s “on” and one that’s “off,” then the snake would be considered heterozygous (hetero = different) for Amel. That looks like this:  a+aa     Because the trait is recessive they will not appear amelanistic but they could pass their “on” gene to offspring who might get another “on” gene from the other parent and result in Amel babies.

Both Stripe and Terrazzo are recessive genes that affect pattern expression. They do roughly the same thing, but the genes sit at different loci on the chromosome and are not interchangeable. If you were to breed a Stripe corn snake to a Terrazzo corn snake, you’d end up with a normal, wild type snake that is heterozygous or “het” for both Stripe AND Terrazzo but visually expresses neither.

Time for dominant traits! A dominant trait needs only one copy of a gene to be in the “on” position to be expressed. These are visually represented by capital letters like this: TTTT Because DOMINANCE.

Whether a snake with a dominant trait is heterozygous or homozygous for that trait, they’ll visually express it regardless. If they are heterozygous, though, they will NOT automatically pass down the “on” copy of the gene to all offspring. This means that a heterozygous Tessera will look have the Tessera look but if they are bred to a non-Tessera snake, only about half of their babies will come out Tessera.

Final Notes: This is a super mega ultra simplified vignette of the bigger genetics picture, and it’s nowhere close to the whole story.    I hope that this tiny peek inspires you to learn more! Corn snakes have been extensively researched and their DNA has been sequenced for study, so there’s a ton of information readily available! I’m sure there will be more yet to come as we continue to learn about these beautiful and fascinating animals.