Im trying to understand the 50%, 66% and 100% Het. I think i got the 50% and 100%, i think. Could someone please explain this to me, im VERY new to all of this
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100% het means the animal is carrying one copy of the gene (typically used for recessive mutations, where two copies are needed for visual expression). 50% het means that one of the parents was 100% het, so each baby in the clutch has a 50% chance of being het. 66% het means both parents were het for that gene, so each baby has a 66% chance that they got one copy of the gene.
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I was close. Thank you for the info!
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Solarserpents explained it well, but to clarify the 66%, if both parents are het, then 1/4 will be visual, 2/4 will be het, and 1/4 will be non-carriers. That means you can leave the visual out of the equation since you know that it carries it, which means that out of the remaining 3, 2/3 or 66% will be het in theory, thatâs where the 66% comes from.
I found that that helped me understand it a bit better when i first learned about it, as 66% seems a bit arbitrary. In reality itâs more like 2x 50% chance for each baby, which in theory results in 66% chance overall.
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Donât worry, @lilace343, you are in lots of company in finding these terms confusing. Good for you for asking.
Used to be the case that people tagged animals as â50% possible het,â or whatever percentage applied. It was often written â50% ph,â which some still use in verbal descriptions. (I do, for one. Itâs even shorter, lol.) Somehow the âpossibleâ got lost and itâs unnecessarily confusing now. I recently spent a long time explaining to someone why their 66% het Diffused animal wouldnât produce 66% Diffused offspring with a visual Diffused mate. Each animal is homozygous, het or not het. Partially het is not a physical option (except for super rare conditions).
Youâve gotten a sound explanation of the genetics. For reading ads and descriptions, when you see the percentage sign just think of it as âpercent chance itâs hetâ whatever trait.
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Yes, I donât like that labeling either. I always put âphâ or âpos hetâ on my animals.
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Personally not a big fan of using percentages in general, like Caryl said if theyâre not obviously a visual, theyâre gonna be either het or non-het, thereâs no inbetween. I personally just use het, pos. het, or likely het (in cases where trait interactions are making it difficult to say for sure, though i do feel like that mainly pertains to cresties where het is being used in relation to certain inc dom traits)
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Lost in the mix lol. I would have never known. I was thinking a percentage not percent chance.
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Hereâs the explanation with examples.
You have an albino female BP you named Marshmallow. You can visually see the albinism. Albino is a recessive trait, meaning the BP needs two copies of the gene for it to be expressed visually. With two copies of the albino gene, it is homogeneous for albino
Then you have a plain old normal male BP you named Zeus. He doesnât have any morph genes in him.
You breed Marshmellow to Zeus and you get an average clutch size of 6. They all hatch beautifully. Every one of these babies will visually look like a normal, but they wonât be normal. They will be what we call âhet albinoâ. This is guaranteed. They will have one copy of the albino gene from mom and one copy of a normal gene from dad. Some people will call these â100% het albinoâ instead of simply âhet albinoâ. I prefer the later. If someone says they are pregnant, you would assume correctly they are 100% guaranteed to be pregnant. You wouldnât ask what percent probability they are pregnant. Anyway, I digress.
Now, if you grow up those het albino babies and breed one of those het albino babies to itâs het albino sibling (I know that sounds grosss, but it doesnât usually cause deformities or medical issues like it would in mammals) and they produce an 8 count clutch that all hatch.
Now of these babies, approximately 1/4 (or two) will be visual albino just like Marshmallow is. These lucky little buggers got one copy of the albino gene from mom and one from dad. The other approximately 3/4 (or six) of the babies would visually look like normals, but looks can be deceiving. Of those six, approximately 2/3 (or 66%) would be het for albino, just like their parents. They would have one copy of the albino gene from one parent and one copy of a normal gene from the other parent. Of those six, the other approximately 1/3 (or 33%) would be plain old normals like Zeus. The problem with those six is, you canât visually tell which ones are het albino or just a plain old normal. But you do know there is a 66% chance that each of those six is het albino. These six would be labeled 66% het albino, as there is a 66% chance that they have one copy of the albino gene. The only way to find out if any of those six are actually (100%) het albino would be to âprove it outâ by selectively breeding them (which would take years) or send a piece of each of their shed skin in for genetic testing.
Hereâs another scenario. You breed one of the original 100% het albino babies back to their mom, Marshmallow. Again, sounds gross but itâs quite common in the BP world and doesnât carry the incest stigma. They have a clutch of 10 eggs that all hatch. Approximately 1/2 (or 5) of the babies would be visual albino just like Marshmallow. The other approximately 1/2 (or 5) would be 100% het albino. Itâs guaranteed that they got one copy of the albino gene from Marshmallow mom (remember mom is a visual albino and therefore has two copies of albino and will therefore always give one copy of albino to all her babies). Itâs also guaranteed that they got one copy of the normal gene from dad. So youâll get an approximately 50/50 mix of visual albinos and 100% het albinos.
And the last scenario, you breed one of the original 100% het albino female babies back to Zeus, the totally normal male BP, and produce a clutch of 12 eggs. All the babies will visually look like normals, but again, looks are deceiving. Approximately 1/2 of the babies will get the albino gene from mom. The other approximately 1/2 will get a normal gene from mom. Zeus will always contribute a normal copy of the gene. So approximately 50% of the babies will have a single copy of the albino gene and the other approximately 50% will be normals. Again, the problem is you canât visually tell the het albinos from the normals. But you do know there is a 50% chance that each baby has one copy of the albino gene. So all 12 of the babies would be called 50% het albino.
Thatâs it in a nutshell. I say approximately a lot above because youâre at the mercy of the odds gods. Itâs possible, but statistically highly unlikely, to breed two (100%) het albinos together and get a clutch of 12 eggs and all 12 of them could be visual albinos. The probability is (0.25)**12 for my fellow math nerds out there. If that happens, go buy a lottery ticket QUICK because you are the luckiest person ion Earth. Itâs statistically most likely to get 3 (25%) visuals from that scenario.
If youâre still confused, do lots of (YouTube) research. Thereâs a huge knowledge base out there thatâs mostly correct. You can learn a lot about BP husbandry, breeding, genetics, etc. from YouTube alone. And of course the folks here are always willing to help without the judgement that comes from other places such as Facebook (so I hear).
If youâre stilll reading this to the end, bless your heart, you must have been really bored. 
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âHalfmoonâ was very thorough in their explanation. That said I would like to add something that may simplify the concept. With recessive genes, there are only three possibilities. A snake is either visual, 100% het, or 100% not het. Those are the only possibilities. As has been stated, but it can get lost in the minutia, is the other percentages or only a âProbabilityâ and nothing more.
When you breed a het animal to a non-het animal, there are only two possibilities. The babies will either be het or non het, period. There is a 50% probability that the babies will carry the gene or not. Itâs a toss of the coin, which has a 50/50 chance of coming up either heads or tails. Now the point to remember is that is just the probability/odds. The reality is out of a six egg clutch, you could get no hets at all, all hets, or any number in between. Each egg has a 50/50 chance just like with a coin toss.
When you breed a het to a het then odds change because there are three possible out comes. Visual, het, or non het. If you get a visual then there is no doubt that the gene is present. As âHalfmoonâ stated, that two other possibilities but it could be a variation of three combinations. The non visuals may be het, but the present gene comes from the male. Het, but the present gene comes from the female. Last and in fact least, non het because neither parent passed the genes. So that means there is a 2 out of 3 chance, or 66% probability that a non visual hatchling carries the gene. Again, be reminded that is just the probability. The reality could be none, all, or any number in between. Once you test a snake or breed it out to prove it, then the snake is proved to be truly het or not Het at all. There are no more percentages.
By way of example, I just paired two animals last season. One was Clown het Hypo and the other was het clown and het hypo. I hit 6 clowns out of 8 eggs even though the probability of a visual clown was 50/50 which indicates that half or 4 should be Clown. I also only hit 1 hypo out of 8 eggs, even the the probability was 1 in 4. So while the probability should have produced 2 hypos, the reality is I didnât. I shed tested 4 of the Clowns to see if they were het Hypo. All 4 were. I donât know if any of the other non-visuals are het since I didnât test them, but what I do know is with the one visual and the 4 hets that tested positive, I beat the odds. I already have 5 out of 8 eggs carrying the gene, and maybe more if I tested everything, but the odds would predict 4 out of the 8 eggs should have the hypo gene present. I hope this is helpful.
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Gotta add a couple things for anybody for whom genetics is a second language and who might be trying to sort this out. First, as point of clarity, the percentages apply to any individualâs odds of carrying a particular allele. These odds do not change for an individual whether one considers at a clutch of twenty, a sample of 500, or a singleton. The ratio of genotypes (which alleles are actually present; absent a genetic test, these are only known by the phenotype they cause) and phenotypes (the visual expression of the alleles present) is known as a Mendelian ratio. Odds are that, across a decently sized sample, youâll see a range of phenotypes which roughly correspond to an expected Mendelian ratio.
Second, the fine explanations given are for the odds of recessive traits. The mechanics of inheritance remain the same for traits which have recessive, dominant or co-dominant patterns of expression but the visual results and the phenotypic ratios differ.
Finally, odds of inheritance are just that. Theyâre not rules. Most breeders who do this a while (and plenty of humans who have never bred any type of animal) will see examples of very long odds happening, in both positive and negative ways.
Edit: fixed typos. Sorry. Vision issues acting up lately.
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I see people and their paragraphs, so Iâm just gonna do a quick version 
Visual x Normal = 100% het
Het x Het = 66% het
Het x Normal = 50% het
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Well, of course! Lol
The original OPâs question was about what those terms mean.
Ah, I didnât see where he asked the term. I thought he just wanted to know how they got the percentages lol. Either way, his question has been answered in great detail, and I think he has all the knowledge he needs 
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. I read it to the end. Thank you
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