Reptile & Amphibian Forums

I'm a little confused on the following corn snake genetics.

If a sunglow is bred to a sunglow then the offspring will be amel right? If that's the case then what if a sunglow is breed to an amel and how do breeders produce sunglows year after year? Are the locus of Amelanism gene moved ever so slightly to create sunglow that it becomes unique only to that animal and if it is bred to another sunglow do the alleles move to a "default locus"?

Bloodreds are diffusion plus line breeding right? So then if a bloodred is bred to a bloodred will the offspring be bloodred?

With pythons if a co-dominant is bred to a co-dominant there is a 1/4 chance of the offspring being super. So then if ultramels are co-dominant does that mean there are super corns?

Finally when dealing with a co-dominant trait how do I predict the offspring's phenotype and genotype properly when it it is being bred to a simple recessive or another co-dominant?

sunglow X sunglow will produce amels and some of them may qualify as sunglow.

I suspect the way to get the most sunglows is to line breed (IE breed sunglows that come from the same line).
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I decided my old sig was too big.

I am not "the" expert but let me try to help clear some of your confusion.
Q:If a sunglow is bred to a sunglow then the offspring will be amel right? If that's the case then what if a sunglow is breed to an amel and how do breeders produce sunglows year after year? Are the locus of Amelanism gene moved ever so slightly to create sunglow that it becomes unique only to that animal and if it is bred to another sunglow do the alleles move to a "default locus"?
So my understanding is that sunglow is a selectively bred amel for less white borders, so to keep a clean sunglow you would bred sunglow to sunglow, if you breed a sunglow to a regular amel you would likely get a less clean sunglow which would be counterproductive if your goal is sunglow.

Q:Bloodreds are diffusion plus line breeding right? So then if a bloodred is bred to a bloodred will the offspring be bloodred?
Bloodreds are also selectively bred diffusion gene, so the answer is similar to the above. If you breed a high quality blood to a lesser quality you would get some variable inbetween. So duffusion and amel refer to the allele of that gene, but bloodred and sunglow refer to selectively bredother desirable qualities to compliment the look of that phenotype.

Q:With pythons if a co-dominant is bred to a co-dominant there is a 1/4 chance of the offspring being super. So then if ultramels are co-dominant does that mean there are super corns?
So with most of the ball python co-dominant genes are refering that those alleles are codominant with the wild type, so example one copy pastel and one wild type copy makes yellow snake and two copies of pastel allele creates super pastel, where as with ultraamels we are refering to ultra allele is co-dominant to the amel allele ate the same loci so one copy of each makes ultramel something in between. Both ultra and amel are recessive to wild type but co-dominant to each other, make sence now?

Q:Finally when dealing with a co-dominant trait how do I predict the offspring's phenotype and genotype properly when it it is being bred to a simple recessive or another co-dominant?
There is not a short answer for this one but there are many, many sources demonstating how to use the Punnet Square to predict offspring, or query Mendelian genetics.

Hope that is helpful, and if I mispoke hopefully one of the more experienced people here will correct me or add to what I have stated.
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Jeff Benfer

1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus

To a large degree I agree with what is said above but wanted to add or qualify a few points.

Sunglow is often amel's which have been line bred for reduced/no white. However I have also heard of some "sunglow" lines which are amel with hypo(both simple recessive) instead of being line bred. Also there is a hypo gene labeled"lava" which has a stronger affect on the melanin and can look like a sunglow as well. Lava is a simple recessive but if you bred a lava to a traditional sunglow you would get normals het for both lava and amel.

Secondly as far as I know there are no Co-Dom genes in cornsnakes. The way I am familliar with Co-Dom genes is that they are dominant over the natural phenotype in the hetrozygous form but that the homozygous form has a phenotype different from the hetrozygous form.

In corn snakes the ultra gene and the amel gene are both simple recessive genes. What makes them behave abnormally is that the ultra and amel genes are co-allelic so if the animal is both hetrozygous ultra and hetrozygous amel then you get the "ultra-mel" phenotype which is a partial expression of each of the genes.

Hope this helps a little.

Sean.
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1.1 BRB
1.1 Triple Het TPRS's
0.1 Silver TPRS
1.1 Amel Bloodred Corns
0.1 Abbott Okeetee Corn
0.1 Blizzard Bloodred Corn
1.1 Thayeri Kingsnakes
0.1 Reeve's Turtle
0.2 Amstaff's
1.0 Pudytat

Sean,
I believe you are somewhat confused as well, co-dominant does not always have relate a morph allele to the wild type allele, as is often the case with most ball python genes that you are obviously familiar with, which some of the ball python morphs that are termed co-dominant would argueably be better characterized as incomplete dominance, however the two terms are somewhat arbitrarily used, especially in the world of snake breeding. The problem is the heterozygous form is usually found first and then the homozygous or "super" form is realized.
Co-dominant can also describes two alleles relating to each other. A classic example of this is human blood groups. As is the case with amel and ultra: one copy amel= wild type phenotype, two copies amel= albino phenotype, one copy ultra= wild type phenotype, two copies ulta= albino like phenotype, one copy ultra one copy amel= albino/albino like phenotype. Having said that ulta and amel are argueably the same or similar alleles at the same albino loci, and are simply very slightly different versions of the same recessive alleles at the albino loci. My understanding is that the ultra/amel relationship is still up for debate, including ultras possible origin from another closely related species of rat snake.
However I do know this; co-dominance does NOT have to relate to wild type only.
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Jeff Benfer

1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus

Not sure how you interpretted what I meant. I actually am virtually completely unfamilliar with ball morphs, they were mentioned by someone else.

The only reason I mentioned natural/wild type is as the basis from which any kind of phenotypic differentiation can occur. The only way something can be described as different, or in this case a expressed trait, is if there is a baseline example(natural/wild type) for which other specimens can be compared to. From what I've always heard/read the "co-" of co-dom was a label for those dominant traits which had a different phenotype when in homozygous form instead of heterozygous. Granted my background is primarily cornsnakes, ratsnakes, and boa's.

I thought incomplete dominance was when a gene is dominant(het/hom) except in the pressence of certain other dominant genes in which case a phenotype differnt from either dominant gene was expressed. The incomplete dominance in this case was that neither gene fully expressed itself but the combination of partialy expressed traits created a third phenotype. If memory serves the example was cow pelt color or something.

I've always heard of two recessive genes at the same loci just being called co-allelic. In the case of ultramels it being the ultra gene and the amel gene.

Also the ultramel is not the same phenotype as amel or ultra last I heard. Ultra was a hypo form and amel is a albino form. I've never worked with them myself but I know people used to visually identify amel's from ultramel's from ultra's within the same clutch.

I have also heard from someone I trust that ultra originated somewhere else. however I don't think it affects the behavior of the gene.

I'm honestly not trying to be arguementative. I am just trying to clarify how I have generally seen it used in the past and how it is used in boa's currently. Not to mention passing allow the correction I recieved when I first inquired about ultra genetics to some of the breeders. If I am wrong or the common practices have changed then I freely accept correction/education.

Sean.
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1.1 BRB
1.1 Triple Het TPRS's
0.1 Silver TPRS
1.1 Amel Bloodred Corns
0.1 Abbott Okeetee Corn
0.1 Blizzard Bloodred Corn
1.1 Thayeri Kingsnakes
0.1 Reeve's Turtle
0.2 Amstaff's
1.0 Pudytat

If you have only one mutant allele or variation of a gene other than the wild type, then yes the characterizations of dominant, co-dominant and recessive are only relating that variants relationship to the wild type, however if you have multiple alleles at the same loci (or gene or set of genes) then those terms are used to characterize the relationship or how they relate to one another. So example if you have alleles A,B,C,D; A could be dominant to B but B is recessive to C, but A is co-dominant with D which is the wild type. These terms are generally used to characterize what is going on at the genotypical level, based on the visual evidence of the phenotype displayed, but sometimes when looked at on a DNA sequence(genomic) and protein sythethis level it is not that simple, but that is a whole "nother" can of worms and it can get very complicated with regards to what is influencing what. That is why a recessive trait with linebreeding as well(ex. sunglow or bloodred), when outcrossing or hets are produced, may or may not carry the line bred characteristics with that trait. Because line bred traits are usually the result of a set of many different blended genes selected to give the resulting phenotype over several generations, rather than a simple on/off switch of one gene or set of genes, the latter being more desireable for the snake breeder to work with because it's easier to control and predict the outcomes.
Sorry so long, hope that makes some sense
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Jeff Benfer

1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus

Here's how we used the terms when I worked in the Ia State Univ Genetics Lab and took the ISU introduction to genetics course.

Both Sean and Jeff are right. The normal gene is the baseline, and a mutant can be compared to the baseline as soon as the mutant is found. Two mutant alleles can only be compared after the second one is found, which could be tomorrow, ten years down the line, or never. So "codominant" either implies or specifies a comparison to another allele. If none is specified, the comparison is always to the normal allele. But either the normal allele or another mutant allele can be specified. "Pastel is a codominant" means the comparison is to the normal allele. "Pastel is codominant to the normal allele" specifies the comparison is to the normal allele. "Amelanistic is codominant to ultra" specifies the comparison is to a second mutant allele.

There is a tendency to restrict dominant, codominant, and recessive to ONLY the relation between a mutant and its wild-type (normal) allele. A two mutant heterozygote like ultramel would simply be described. For example, Ultra and amelanistic are recessive mutant genes. The ultra//amelanistic heterozygote is more or less intermediate in color between the ultra homozygote and the amelanistic homozygote. That last sentence is a lot longer and less convenient than "Amelanistic is codominant to ultra." In my opinion, the convenience will make people retain the "amelanistic is codominant to ultra" useage.

For simplicity, codominant and incomplete dominant can be used as synonyms. If you really want to get technical, the concept can be subdivided into at least three and probably more terms. Of course, that requires knowing something about the biochemistry. And we know very little about the biochemistry of reptile mutants. Many people on these forums have little knowledge of genetics, so I go with simplicity.

The Punnett square is a good learning tool but has drawbacks for heavy duty use. The pro geneticists I worked for hardly ever used the square. They did one gene pair problems in their heads and used the branching system (AKA decision tree, forkline) for two or more gene pairs. It gives the same answer, is quicker and is less prone to mistakes. It is a little less intuitive than the Punnett square, though. Unfortunately, I haven't found a good description on the web of a branching system applied to a genetics problem.

Paul Hollander

Paul,
As far as I can see you just stated exactly what I already stated, maybe slightly different wording, but the points are exactly the same, so I would say we are in total agreement. I am a Biochemist/Molecular Biologist working as a Public Health Microbiologist in the Virology/Molecular Biology Department at the State Health Lab for Iowa aka University Hygienic Laboratory, I too am an ISU and UofI grad. are you still living in Iowa? I am near Iowa City.
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Jeff Benfer

1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus

Hi Jeff. Yes. I'm a technician in the ISU chemistry dept now.

Paul Hollander

When you mention branchin/decision tree are you just reffering to the statistical probability view of a combination?(although this is as easily done in the head also)

for example a (triple het) x (double hom single het) offspring being (triple hom) = 1/2 x 1/2 x 1/2 x 1/2 = 1/16 or trait by trait = 1/2 x 1/2 x 1/4 = 1/16

Or are you talking about something completely different? Just wondering since my Mathematics background is much more extensive then my Bio/Chem background.

If it is something else then do you have any sights that have information on it?

Sean.
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1.1 BRB
1.1 Triple Het TPRS's
0.1 Silver TPRS
1.1 Amel Bloodred Corns
0.1 Abbott Okeetee Corn
0.1 Blizzard Bloodred Corn
1.1 Thayeri Kingsnakes
0.1 Reeve's Turtle
0.2 Amstaff's
1.0 Pudytat

Thanks for the info. But how can you tell if a bloodred will be a high quality bloodred when it is a hatchling?

While on the subject of bloodreds I read that they can be picky eaters, so how difficult are new born hatchlings to start feeding? In other words are they as picky as a hatchling alterna?

when looking for baby bloodreds i usually pick the ones with grey heads and the most washed out pattern on its sides. different people like different things... but like all hatchlings its hard to tell which will make a nice adult.

~kin
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Best indicator may be what the parents look like - but even that doesn't always work.
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I decided my old sig was too big.