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The Cultivars (morphs)/Genetics Issues Discussions about genetics issues and/or the various cultivars for cornsnakes commercially available.

Genetics Tutorial
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Old 10-14-2006, 07:24 PM   #1
Genetics Tutorial

Originally Posted by gwb8568
that would be awesome......i have loves book along with two other "corn/rat snake" books and read them all. sometimes things make sense, but as soon as another thread starts and the discussion get going......... i'm out.
i never followed biology through high school or college, and not being conceted, i was smart enough to get an academic scholarship along with an athletic. but when the topic turns to genes/traits/hets/homos/hypos/etc........ there i go again. all i know of as right now after being here for 8 months is that: amel lacks the blacks and anery lacks the reds. and i even have to picture my anery when i think it to my self to make sure i am not talking about the other.
and more thing that is very confusing is this from my "Corn Snakes and other Rat Snakes" book by Bartlett. This is what is stated in shorter terms: Corn Snake species....normal, okeetee, miami, rosy rat and kisatchie. Designer Corn Snakes........axanthic, amelanistic, blood-red, amelanistic (white albino), sunglow, candy cane, snow, ghost, blizzard, hypomelanistic, christmas, butter, pepper(pewter), lavender, amber and caramel. Pattern Mutations......motley, striped, aztec, milk snake phase, creamsicle and candy cane. now how in the hell can a candy cane be a "color" or "morph" AND also be a pattern....... now i don't understand all of the above and even after reading it over and over and over i still have some learning to do, but that last one throws me. i can deal with not knowing what you need to get a certain type snake (ultramel, granite, etc.) but i have yet to find a way to make it "stick". now granted next year i will be breeding for my first time (with pcar/paul) so once we mix up some parents and i get to see the results, it might make more sense to me then. but in the mean time, does anyone have like a 3rd or 4th grade level book on genetics.

sorry to "hijack" the thread as i was going to start one on my own, but with the replies that are sure to come after this post and the title being "hets" i thought that this might end up being a good thread for everybody who would like to learn. thanks again susan.
It sounds like the book you're reading is possibly an "old" one. In the very least, it's a bit inaccurate. The list of cornsnake species is the first mistake. There are a couple of sub-species, and even those will vary as to the source and when the information has been published. But Okeetee and Miami phase are simply selectively bred "looks" of normal (wild-type) cornsnake coloration...not seperate sub-species, let alone seperate species!

And as for the pattern mutations, milksnake phase and candycane are again, selectively bred looks that can affect the pattern, especially the milksnake phase, but they are not created by a recessive gene like motley and diffusion is. Zigzag/aztec is a pattern mutation, but exactly what and how many genes are invloved with the look has yet to be determined. And as for creamsicle...that is a hybrid, not a cornsnake morph. A creamsicle is a cross between a cornsnake, (Pantherophis guttata - formerly Elaphe guttata guttata) and a Great Plains rat snake (aka Emoryi's rat snake - Elaphe guttata emoryi - I'm not sure if they changed the scientific name for that one too).

I know the basic genetics have been discussed on this forum multiple times, but it's obvious that some people are still having trouble understanding it. In some cases of learning difficulties, it's simply how the information is presented. Therefore, I'll give it a whirl and maybe one more person will have that light bulb glow over their head. Just bare in mind that I sometimes have a habit of rambling and please forgive me when I do it. I'll be giving my tutorial in multiple replies in this thread. Feel free to intervene with questions at any time.
Old 10-14-2006, 08:38 PM   #2
Lesson 1

Charles Pritzel has written 2 editions of an excellent book covering cornsnake genetics and morphs titled the Cornsnake Morph Guide . It is available for purchase from Cedar Creek Corns. You can use this link to their website: I don't intend to get as technical as the book, but instead will just try to explain the basics. With the basics understood, using Serp's book for the details won't totally turn your brains into mush. The progeny predictors will also perhaps make more sense.

Now let's start.

When talking about any of the multiple cornsnake morphs, it is always "compared" to what is considered the normal, or "wild-type" cornsnake. All of the genetic morphs are recessive to the dominant normal/wild-type gene. Genes are the blueprint for what the snake will look like. They work in pairs. An individual gets one gene from it's mother and one from it's father. As a very broad example, the sex of humans is determined by the X and Y chromosomes. A woman is XX and a man is XY. The mother can only give an X to her offspring...she is "homozygous" or "homo" X. The father can give either an X or a Y...he is "heterozygous" or "het" Y. The principle is generally the same when discussing homo and het cornsnake genes. Homozygous means there are 2 of the same gene present. Heterozygous means that the 2 genes in the pair are different.

The normal/wild-type genes are dominant over the recessive morph genes. Genes, for use in the Punnett square, are labeled as a letter of the alphabet. Normal/wild-type/dominant genes use the capital letter. The "corresponding" recessive gene(s) that occupies the same place as that dominant gene is written with the lower-case version of the letter. For example:

In the normal corn, the gene pair that says to produce black pigment is AA. The recessive gene pair that says NOT to produce black pigment (to make the snake an amelanistic) is aa. If a normal (AA) is bred to an amel (aa), each snake can only pass on their version to the offspring. Those offspring would be written as Aa. Since the normal gene is dominant over the recessive gene, and the snake possesses one gene to produce black, the snake will be normal in appearance (phenotype) but will be normal het amel in genotype.

The same thing would happen when any or all the recessive corn genes are used. For example:
aa - says don't make black - produces an amel
bb - says don't make red - produces an anery
hh - says reduce the amount of black - produces a ghost
cc - says to change alot of red to yellow - produces a caramel
dd - says to create the diffuse pattern - produces diffuse/bloodred
mm - says to create the motley pattern - produces a motley
ss - says to create the stripe pattern - produces a stripe
ll - says to create the lavender appearance - produces a lavender
And you can use whatever letter you want for these morphs as well as all the other recessive morphs.
All of the genes, in either the dominant or recessive form, are found in each and every cornsnake. However, not all may be used when writing a genotype for an individual, only those that will potentially affect the appearance away from the normal or may be passed to offspring.
For example: a hypolavender motley would be written as hh ll mm instead of AA BB hh CC DD ll mm.

If I were to breed that hypolavender motley to a diffuse opal (aa dd ll), I would show the combined genes for the pair:
hypolavender motley - AA hh DD ll mm
diffuse opal - aa HH dd ll MM

The resulting offspring from this pairing would all be lavender het for amel, hypo, diffusion and motley (Aa Hh Dd ll Mm) as the only morph gene that is the same in each parent is lavender. I will show this pairing in a Punnett square in my next reply. Right now, I need a cup of coffee!
Old 10-14-2006, 09:01 PM   #3
The Punnett Square

This is the fun part! least for me it is. If you get this, you won't ever have to use a progeny predictor again. You may get writer's cramp, however.

The Punnett square is a handy dandy tool used to figure out all the different gene combinations that can result from a specific pairing. The more genes you work with, the larger your square will be (and the greater potential offspring...genotypically anyway).

Starting simply: Normal X Anery (BB X bb)

Each parent can only give 1 gene to the offspring. One parent's gene(s) are written along the top of the square (columns). The other parent's gen(s) are written along the side (rows). The above pairing would look like this:

.....B / B
b / Bb Bb

b / Bb Bb

All the offspring are normal het anery (Bb).
Also, most people, in the above case, would only show one of the same gene (one column of B and one row of b).

Adding another gene into the mix: Normal (AABB) X Snow (aabb - amel & anery)

ab / AaBb

All the offspring are normal het amel and anery (AaBb - also called het snow).

Now lets do that hypolavender motley X diffuse opal...

................A h D l m
a H d l M / Aa Hh Dd ll Mm

As you can see, the dominant gene (capital letter) is always written first, no matter which parent it came from (as indicated by color). All the offspring are lavender het amel, hypo, diffuse and motley.

Of course, when each gene in each parent is homozygous, it's easy to do the square. The REAL fun begins when you have heterozygous gene pairs! That will be the next lesson...need more coffee!
Old 10-14-2006, 09:51 PM   #4
Oh Goody! ....Hets!

OK...if you're still with me, I'll add a single het gene into the mix:
Normal X Amel het anery (AABB X aaBb)

The normal can still only give 1 version of each gene. However, the amel can give not only the normal version of B but also the b version to produce anerythrism. The columns will stay the same as before, but watch what has to be done now with the rows:

aB / Aa BB
ab / AaBb

All the offspring are still normal phenotypically, but genetically, half of them are normal het amel and half are normal het amel AND anery. Since you can't tell visually which babies are het for anery and which are not, all of these hatchlings would be labeled normal het amel 50% het anery (normal all het for amel, but each has a 50% chance of being het for anery).
Old 10-14-2006, 10:10 PM   #5
Multi-Hets! Even Better!

We've now held back a trio (1.2 - 1 male, 2 females) of these babies, fed and cared for them for 3 years, and finally bred them. After waiting what seems like forever, you finally get pippies. When all is said and done, you have from one clutch 16 normals and 5 amels. The second clutch produced 11 normals, 2 amels, 4 anerys and 2 snows. With this information, and knowing what the original pair was, you now know the genetics of your trio. The male is normal het amel and anery. So is the one female. The other female, however, is only het amel (or Murphy is playing games with you, which can happen, however unlikely).

To prove my theory with the punnett square:
Normal het snow X Normal het snow (AaBb X AaBb)

AB / AABB...AABb...AaBB...AaBb
Ab / AABb...AAbb...AaBb...Aabb
aB / AaBB...AaBb...aaBB...aaBb
ab / AaBb...Aabb...aaBb...aabb

Each snake has 4 different possible gene combinations. Each of these 4 has an equal chance of being paired with any of the 4 combos from the other snake. 4 X 4 = 16 possible combination chances.

According to the square, your odds for each genetic combination is as follows:
1/16 - AABB - normal
2/16 - AABb - normal het anery
2/16 - AaBB - normal het amel
4/16 - AaBb - normal het amel and anery
1/16 - AAbb - anery
2/16 - Aabb - anery het amel
1/16 - aaBB - amel
2/16 - aaBb - amel het anery
1/16 - aabb - snow (amel anery)

Phenotypically, you get 9/16 normal, 3/16 anery, 3/16 amel and 1/16 snow. The offspring from the second clutch follows these odds fairly well. When labeling these offspring, you again cannot be certain of the exact hets each hatchling can be carrying. Therefore, since 6 out of 9 (2 out of 3 or 66%)normal hatchlings could be het for either amel, anery or both, they would be labeled as normal 66% het amel and/or anery. The same goes for the amel and anery offspring (2 out of 3)...amel 66% het anery and anery 66% het amel.

The first clutch writes out as this:
Normal het snow X normal het amel (AaBb X AaBB)

Ab / AABb...AaBb
aB / AaBB...aaBB
ab / AaBb...aaBb

One snake has 4 different gene combinations while the other only has 2 different combinations. 4 X 2 = 8 possible combination chances.

Again, according to the square, your odds are:
1/8 - AABB - normal
1/8 - AABb - normal het anery
2/8 - AaBB - normal het amel
2/8 - AaBb - normal het amel and anery
1/8 - aaBB - amel
1/8 - aaBb - amel het anery

Phenotypically, you 6/8 (3/4) normals and 2/8 (1/4) amels. The first clutches' hatchlings match the odds. Labeling these offspring would be a bit different than the other clutch. The normals have a 4 out of 6 (2 out of 3 or 66%) chance of being het for amel, but only 3 out of 6 (1 out of 2 or 50%) chance of being het for anery. Therefore, they are normal 66% het amel 50% het anery. The amel offspring are all 50% het anery (1 out of 2).

OK...I definately need more coffee!
Old 10-14-2006, 11:00 PM   #6

Just stuck a photo of Persius, my male pewter in, to give you a break. I'll also stop for awhile to give anyone a chance to ask questions or for further/different explanations, etc.
Old 10-15-2006, 12:27 AM   #7
More Multi-Hets where did I leave off...Multi-hets! The size of your Punnett square will depend upon how many genes you want or need to deal with. The more hets you have to play with, the larger your square and the more your hand will hurt when you're done. And I'm afraid to say that the size can increase exponentially. For example, back to that hypolavender motley X diffuse opal pairing. Their offspring are easy to identify phenotypically and genetically. However, breed a pair of those offspring together and be prepaired for a head-ache! Each of those new parents (Aa Hy Dd ll Mm) can potentially give to their offspring the following gene combinations:
A H D l M
A H D l m
A H d l M
A H d l m
A h D l M
A h D l m
A h d l M
A h d l m
a H D l M
a H D l m
a H d l M
a H d l m
a h D l M
a h D l m
a h d l M
a h d l m

16 X 16 = 256 possible combination chances. Luckily there is some duplication going on, and the phenotype possibilities are even less...but still...

Ready to cross a diffuse Sunkissed phantom stripe with a lava caramel lavender motley...and then see what you'll get in the F2 generation? You go right ahead! I'm too tired tonight and will move on to the couple of problem genes.
Old 10-15-2006, 01:15 AM   #8
Motley and Stripe & Ultra and Amel

Gotta love these 4 genes! I know I do. Once you get the idea that you treat motley and stripe, as well as ultra and amel, as if they were a married couple, you'll have better luck. I like to think of the motley and stripe couple as Archie and Edith Bunker (for those old enough to remember All in the Family). The motley and stripe gene live in the same house (are located at the same locus). The stripe gene (Edith) is very sweet and loving. You can always count on her to do the right thing...produce lovely stripes when she's with another sweet lady (stripe gene - ss). The motley gene (Archie) can be very unpredictable. You know that something stupid is going to come out of his mouth, especially when paired with another motley George Jefferson (you'll get a motley pattern - mm) but you really can't predict what the stupidity is going to be about (nice motley pattern, Q-tip motley or a striped motley). Put Edith and Archie together (mm X ss = ms) and Archie's domineering, loud-mouthed bigotry will rule (Just shut up and get me a beer!). That is, when you have 1 motley and 1 stripe gene together, the motley pattern will over-ride the stripe pattern.

Cube fits in with motley and stripe somewhere (probably the Meathead, but I'll put my bet on Gloria), but it really hasn't been figured out yet.

Ultra and amel are very similar except they are more like Steve and Elyse Keaton (the parents) on Family Ties. They also live in the same house but instead of one being the head of the household, they're extreme liberals and each has an equal voice in everything. Put 2 ultras together (uu) and you ultra. Put 2 amels together (aa) and you get...class? An amel...right! Put an ultra with an amel...they combine ever so sweetly (ua) and you have an ultramel...something that isn't fully one or the other, but rather an equal combination of the two.

When you breed an ultramel (ua) or a motley/stripe (ms) to a normal, the offspring will only be het for one or the other trait...never both.

AA X ua = Au (or Uu) and Aa

MM (or SS or even MS - all the same thing, just different letters) X ms = Mm and Ss

Also, breed an ultramel with an amel, you will get ultramel and amel offspring...but please note that the amel offspring are just like any other amel produced from any cornsnake carrying the amel gene. DO NOT spend more money on one simply because it is marketed as being from an ultramel parent.

Now I'm going to bed. I may or may not add more to this tomorrow. It may depend upon if I find any questions or not.
Old 10-15-2006, 12:14 PM   #9
Originally Posted by Susan
When talking about any of the multiple cornsnake morphs, it is always "compared" to what is considered the normal, or "wild-type" cornsnake. All of the genetic morphs are recessive to the dominant normal/wild-type gene.... The normal/wild-type genes are dominant over the recessive morph genes.
Correct me if I'm wrong, but I'd been under the impression that this is not always the case. We may someday discover a corn snake 'mutant' gene that is dominant or codominant to 'wild type' (and 'bloodred/diffuse' may actually already qualify if you get visual hets).

I know that, in mice, there's a mutant gene producing tan bellies that is visible even on wild-type Agouti.

Granted, the majority of known morphs are simple Mendelian recessives.
Old 10-15-2006, 01:35 PM   #10
o.k................i finally found it. just wanted to thank you for doing this for me (and future others also). i know it took alot of time to put together and type, thanks again. i have glanced through it and am going back to the top of the page (1) to thoroughly read your entire posts. just wanted you to know that i did find it and many thanks.

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