| Genetics |
A Crash Course In Genetics:When reading about morphs and genealogy, it’s sometimes hard as a beginner to understand what is meant by phrases like:100% Het 66% Het 50% Het Heterozygous Homozygous Double Het Triple Het Poss We’re going to break it down in simpler terms. Read slowly. All genes are paired genes. Genes are either dominant or recessive (There IS such thing as co-dominant, but for argument sake, let’s skip that lesson until later). A dominant gene is a trait that’s shown. A recessive gene is a gene, that only when paired with another recessive gene, will it be seen. Let’s take brown-eyed people and blue-eyed people. The color brown in eyes is a dominant gene. The color blue in eyes is a recessive gene. When two alike genes are paired together, it’s called being Homozygous. Brown eyes will be labeled BB (homozygous for brown eyes) and blue eyes will be labeled bb (homozygous for blue eyes). When a brown-eyed person and a blue eyed person have children, the possible outcomes are:
There are 4 possible outcomes, and as you can see they are all the same (Bb). What this will show is that any child born will have brown eyes. Even when brown is paired with blue, you will only see brown because brown is a dominant gene. But any child born from a brown-eyed and blue-eyed parent CARRIES the gene for blue eyes. This is called being Heterozygous for blue eyes. These children have a 100% possibility of being Heterozygous for blue eyes (4/4 = 100%). Now, when this is compared with, say, an Albino Ball Python, Albinism is the recessive gene. Albinism is a lack of all black pigment. AA will represent a regular Ball Python, and aa will represent an Albino Ball Python. When a regular and an albino are bred together, you will get:
This means that all the snakes hatched will look normal, but will carry the gene for albinism. This is called being Heterozygous for Albino. Each snake hatched will have a 100% possibility of being Heterozygous for Albino (4/4 = 100%), or 100% Het Albino as is commonly referred to in the pet trade. Now, if two 100% Hets were bred together, the outcome would be:
This means that each egg has a 25% chance of being homozygous for Albino (1/4 = 25%), 25% chance of being homozygous for normal (1/4 = 25%), and 50% chance of being heterozygous (2/4 = 50%). Unfortunately, because Hets look like normals, we can’t be sure if they’re Hets or not. There are 4 possible outcomes demonstrated by the table above. Take the obvious albino away, now all that remains are 3 outcomes, 2 of which are het. So, when two 100% Hets are bred together, each hatchling that is normal looking has a 2 out of 3 chance of being heterozygous (2/3 = 66% Possibility), or 66% Poss Het Albino. The only way to positively prove a 66% Poss Het Albino is actually a carrier of the albino gene (which will prove it to be 100% Het Albino) is to breed it to an Albino:
If it really is a carrier (Aa), then statistically half the hatchlings will be albino and half will be normal looking. If the snake is not a carrier (AA), then all the offspring will look normal. If a 100% Het Albino is bred to a normal, then the outcome would be:
This means that each hatchling has a 50% chance of being normal and 50% chance of being a carrier. They will all look normal, so again, 2 out of the 4 outcomes are Hets (2/4 = 50% possibility), or 50% Poss Het Albino. Again, the only way to prove it really is a carrier is to breed it to an albino. The reason any possible Hets should be bred to an albino to prove they really are carriers is that it eliminates other possibilities. You’re going to get Albinos and 100% Het Albinos if it’s a carrier, and only 100% Het Albinos if it’s not. Though, if someone just wants to have a breeding project, possible Hets are much cheaper than 100% Hets and not much more expensive than a normals. The chance of getting albinos or any other morph will make the breeding project much more fun for any novice or hobbyist. The best project is to use one or two 100% Het males and a group of 66% or 50% Poss Het females. The morph you want will be floating around in there somewhere. |
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Now, getting into slightly more difficult genetics, there’s what’s called Double Hets. This is a normal looking snake that is a carrier for TWO recessive genes. This happens when two morphs are bred together. Let’s take a Piebald and an Albino for example.
pp=Piebald (recessive) PP=Not Piebald (dominant) aa=Albino (recessive) AA=Not Albino (dominant) A Piebald doesn’t carry the albino gene, so it will be labeled ppAA, and an Albino doesn’t carry the Piebald gene, so it will be labeled PPaa. So, when a Piebald and an Albino are bred together, the outcome will be:
When these genes are added together, the results are:
As you can see, all the outcomes are the same (PpAa). Each egg hatched from breeding a Piebald to an Albino will have a 100% chance of carrying both genes (16/16 = 100%), but will look normal. This means they are 100% Double Heterozygous for Albino Piebald. The ultimate goal in doing this is to have both recessive genes expressed, and the odds of this when breeding two Double Hets together is:
There is only a 1 in 16 chance of getting an Albino Piebald. The others will be a mess Albinos, Piebalds, normals, Hets, and Double Hets that will be indistinguishable. But for argument sake, here are the percentages: 1/16 chance of getting an Albino Piebald 3/16 chance of getting a Piebald w/ 66% Poss Het Albino 3/16 chance of getting an Albino w/ 66% Poss Het Piebald 9/16 chance of getting a Normal w/: 44% Poss Double Het Albino/Piebald 66% Poss Het Albino 66% Poss Het Piebald Then there’s what’s called Triple Hets. Granted, the chances of getting an Albino Piebald (homozygous for two recessive genes) are slim as it is, this is all in theory. If you had an Albino Piebald, it can be bred to yet another recessive morph like Patternless. pp=Piebald (recessive) PP=Not Piebald (dominant) aa=Albino (recessive) AA=Not Albino (dominant) ll=Patternless (recessive) LL=Patterned (dominant) An Albino Piebald doesn’t carry the Patternless gene so it will be labeled ppaaLL and a Patternless doesn’t carry the Albino or the Piebald gene, so it will be labeled PPAAll. When an Albino Piebald is bred to a Patternless, the outcome will be:
Without making a 64 square table, I can state that all the outcomes will be the same (PpAaLl). This is being 100% Triple Heterozygous for Patternless Albino Piebald, though every snake will look normal. If two triple hets are bred together, then the possibility of getting a Triple Homozygous for recessive genes (ppaall or Patternless Albino Piebald) is 1 in 64. With Ball Pythons only laying 5 to 8 eggs, this is near impossible. If you thought that there was a mess of morphs and hets with just trying to breed double hets, here’s what’s left over when breeding triple hets: 1/64 chance of getting a Patternless Albino Piebald 3/64 chance of getting an Albino Piebald w/ 66% Poss Het Patternless 3/64 chance of getting a Patternless Albino w/ 66% Poss Het Piebald 3/64 chance of getting a Patternless Piebald w/ 66% Poss Het Albino 9/64 chance of getting an Albino w/ 66% Poss Het Piebald, 66% Poss Het Patternless 9/64 chance of getting a Piebald w/ 66% Poss Het Albino, 66% Poss Het Patternless 9/64 chance of getting a Patternless w/ 66% Poss Het Albino, 66% Poss Het Piebald 27/64 chance of getting a Normal w/: 30% Poss Triple Het Patternless/Albino/Piebald 44% Poss Double Het Albino/Piebald 44% Poss Double Het Albino/Patternless 44% Poss Double Het Patternless/Piebald 66% Poss Het Albino 66% Poss Het Piebald 66% Poss Het Patternless This is a little ridiculous, but having a Triple Het gives you the opportunity to have a snake that when bred to any of these three morphs, heterozygous or homozygous, you’re going to get those morph babies (with the possibility of having a few special genes floating around in there). Also, when bred together, they will give you these three morphs. Now if you really wanted to make a Triple Homozygous, the ‘easiest’ way to do it is to breed two Double Homozygous morphs together that have one similar morph each. If you bred an Albino Piebald to an Albino Patternless, you’d get Albino babies that are Double Het for Patternless Piebald. When two of these are then bred together, you’ll have a 1 in 16 chance of getting a Patternless Albino Piebald. Most morphs are recessive genes. There are the occasional co-dominant genetic morphs though. Co-dominant genes are genes in which both in the pair are visible, so it’s easier to breed. Let’s say there was a gene that made everyone 8 feet tall (HH) and a gene that made everyone 4 feet tall (SS). If someone were HS then they would be 6 feet tall. It’s an average of both. HS is created using the same breeding principles as above, just the “% possibility” factor doesn’t exist because the trait is visible. Here is an example of a co-dominant gene with the infamous Reticulated Python: Normal Pattern (NN) Tiger Pattern (NT) Super Tiger Pattern (TT) An example of a co-dominant morph in ball pythons is the Pastel (heterozygous) and then the Super Pastel (homozygous). Then there are dominant morphs. Remember how the normal gene is dominant over the albino gene? In some cases the morph gene is dominant over the normal gene. This is apparent in the Spider morph. A majority of the Spiders available are heterozygous, but look like a Spider. A homozygous Spider looks just like a heterozygous Spider. When a Spider Het is bred to a normal the possible outcomes are:
Each egg has a 50% chance of being a visible Het Spider and a 50% chance of being normal. Statistically, when a Het Spider is bred to a normal, half the hatchlings will be Het Spider. When two visible Het Spiders are bred together, the possible outcomes are:
Each egg has a 25% chance of being homozygous for Spider (SS), 50% chance of being heterozygous (NS), and a 25% chance of being homozygous for normal (NN). Because Spiders look the same as Het Spiders, we can't be sure if the Spiders hatched are Hets or Homos (please no jokes... hahaha too late). There are 3 possibilities getting a Spider, 1 of which is a homo. So, when two Hets are bred together, each hatchling that is a Spider has a 1 out of 3 chance of being homozygous (1/3 = 33% Possibility), or 33% Poss Homo Spider. A majority of co-dominant and dominant morphs when homozygous are called Super Whatever, like Super Pastels or Super Spiders or Super Tigers. For Spiders, the only way to prove it to be a "Super Spider" is to breed it to a normal, because if a Spider is homozygous, all the offspring will be Spiders, and if a Spider is heterozygous, you'll get Spiders and normals. Popular Ball Python Morphs and Mutation: Albino: Recessive Axanthic: Recessive Black/Chocolate: Co-Dominant (Heterozygous forms are Black Pastel, Cinnamon Pastel, Labyrinth) Caramel Albino: Recessive Clown: Recessive Derma: Recessive Ghost: Recessive Ivory: Co-Dominant (Heterozygous form is Yellowbelly) Lavender Albino: Recessive Leucistic (Blue Eyes): Co-Dominant (Heterozygous forms are Platinum, Mojave, Phantom, High Yellow Lemon Leucistic (Black-Eyes): Co-Dominant (Heterozygous form is Fireball) Pearl: Co-Dominant (Heterozygous form is called Woma) Pastel: Co-Dominant (Homozygous form is called Super Pastel) Patternless: Recessive Piebald: Recessive Pinstripe: Dominant Red Axanthic: Co-Dominant (Heterozygous form is called Black Back) Spider: Dominant Spotnose: Co-Dominant (Homozygous form is called Super Spotnose) Stripe: Recessive |
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