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

Best Way to Test an Invisible Gene...? Halo corn snakes
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Old 03-21-2019, 11:34 AM   #1
scmartin27
Best Way to Test an Invisible Gene...? Halo corn snakes

The title may be a little misleading. But I'll explain.
First: If you have not read my forum thread about HALO corn snakes, you may want to start there. Yes it's long, I'm sorry!
I'll summarize here so those who don't want to be fully educated can at least get the gist and offer some reasonable advice.
"Halo" is the term we've been using for the yellow borders that show up in many amel types. Most commonly snows - but I've also seen it in regular amels, fires, blizzards, lavamels, peppermints, scaleless amel types, and others (so far not lavender, however, which isn't surprising to me). I'll attach photos of some examples. The issue with testing this gene is that it is not visible in anything with melanin.
After doing a few trials I *believe* it to be dominant or incomplete dominant... with the possibility that Green Blotched (where the yellow completely covers the saddles, sometimes looking green) is the homozygous version if it is incomplete dominant.

Now on to the actual meat of the question: how do I test this with a WC? Though it may be dom/inc-dom, we can't see it in the F1s since they would all have full melanin. Breeding the offspring back together doesn't help our case either - all that would prove is that it can be passed on, but not specify if it is dom, inc-dom, or even recessive (which all signs point to it NOT being, so far).

So... any suggestions here? Again, before commenting with what you think should be done you may want to read my other post about Halos (http://www.cornsnakes.com/forums/sho...d.php?t=145967). I've done many breeding trials already... but have been told by many that nothing is proven til it's bred straight to a WC. or something like that

Thanks for any input!
 
Old 03-21-2019, 01:49 PM   #2
67temp
I've read your other post in the past. Could you do a normal snow with no signs of halo bred to a wild caught. The babies would then be normal 100% het for amel and anery. Take some of those normal babies and test breed them with your halos, if you get amels or snows that then show signs of the halo it shows that the halo got passed down in a dom/inc-dom manner.
 
Old 03-21-2019, 06:19 PM   #3
Dragonling
Quote:
Originally Posted by 67temp View Post
I've read your other post in the past. Could you do a normal snow with no signs of halo bred to a wild caught. The babies would then be normal 100% het for amel and anery. Take some of those normal babies and test breed them with your halos, if you get amels or snows that then show signs of the halo it shows that the halo got passed down in a dom/inc-dom manner.
I would think you'd need to take it one step further and breed those offspring together. Pair a suspected homozygous Halo male to the WCxSnow female offspring, then pair the Amel or Snow hatchlings together to see what range of phenotypes you get in the F3s. Eesh...talk about time investment...
 
Old 04-05-2019, 03:18 PM   #4
scmartin27
Time investment indeed...

It seems to me that if I had a WC x Snow, then bred those babies together to get an amel or snow, then bred THOSE amels/snows to a halo then we would find out. So yes, basically what you said - Dragonling.

I've already done a WCxSnow offspring (so a classic het snow from a WC parent) to a halo, though. And got half halos and half non-halos in the amel based offspring. I just didn't breed a potential homozygous one to her, just a heterozygous one (or assumed to be het, anyway).

The only Green blotched I have is female... so maybe I just need a snow male with no yellow to breed her to? Does WC *really* have to be involved here? (honestly looking for opinions on that)

I suppose I could breed the Green blotched to a normal from the WC x Snow pairing to see if all amel based offspring end up being halos. But that means only ~1/2 the offspring would "count" and I'd have to do twice as many trials to determine it. not to mention... the yellow is hard to see in the amels til they're literally adults. it's easier to see it in the snows when they're young because there's no other pigment to contend with. But with Amels that yellow can stay hidden for years.

So again I ask... does a WC *Really* need to be involved? If not, I'll find me a male snow with no yellow and try him out with my gb girl next season.
 
Old 05-13-2019, 06:13 PM   #5
paulh
Seems to me that the halo gene could be a modifier gene. "Individuals with a double mutant combination of modifier and target mutation have either a reduced (suppressor) or or more severe (enhancer) mutant phenotype. Many modifier genes produce a different phenotype from their target mutation, and some produce no mutant phenotype at all when the mutant allele of the target gene is not present." (From Atherley, Girton and McDonald, The Science of Genetics. Saunders College Publishing, 1999. ISBN 0-03-029232-8.) When the mutant allele of the target gene is not present, the wild type allele of the target gene is present. So analysing the inheritance relationship of the mutant modifier gene to its wild type allele requires the presence of the mutant allele of the target gene to be present.

Also, there is a difference between WC (wild caught) and wild type (WT). Wild type (AKA normal) = 1) the most common phenotype in the wild population; 2) the most common allele of a given gene in the wild population. A wild caught creature probably has a wild type phenotype/genotype and was captured in the wild. A wild type creature can be a million generations captive bred as long as it has the wild type phenotype/genotype. Wild type at the modifier gene's locus is required. Wild type at every locus is usually helpful but not required. Wild caught is not required.

A couple of more definitions:
Allele = one of two or more versions of the same gene. Alleles have the same genetic locus. Two alleles can form a gene pair. Example: In the corn snake, the motley gene, the striped gene and the corresponding normal gene are alleles. And the amelanistic gene, the ultra gene and the corresponding normal gene are alleles. However, the amelanistic gene and the motley gene are not alleles because they do not have the same locus.
Locus (plural--loci) = A particular gene's location in the genome (chromosomes/DNA in a sperm or egg). Although there are exceptions, most genes keep the same locus over the generations.

Wild type is piecemeal in nature. A given corn snake may have two amelanistic alleles at the amelanistic locus and still have two wild type alleles at the anerythristic locus and at the caramel locus and at the motley locus.

You are saying that the halo mutant allele has a locus that is independent to the amelanistic and anerythristic genetic loci, Halo phenotype occurs when a halo allele is paired with the corresponding normal allele, and green blotched is produced when the gene pair has two halo alleles. Can green blotched be identified in amelanistic corns, or does it require snow to show up? What is commonest in snow corns--non halo, or halo/green blotched? If non halo, that is the wild type allele's phenotype. Once you assign the wild type phenotype, you just need numbers and breeding results to determine whether the halo allele is dominant/codominant/recessive to the wild type allele. Matings: non halo snow with at least one halo or green blotched parent x non halo snow with at least one halo or green blotched parent, halo snow x non halo snow, halo snow x halo snow, green blotched snow x green blotched snow, green blotched snow x halo snow, green blotched snow x non halo snow. Record total number of eggs, total number raised to age where non halo, halo or green blotched can be identified, number of non halo, halo and green blotched.
 
Old 05-14-2019, 10:47 AM   #6
scmartin27
Quote:
Originally Posted by paulh View Post
Seems to me that the halo gene could be a modifier gene. "Individuals with a double mutant combination of modifier and target mutation have either a reduced (suppressor) or or more severe (enhancer) mutant phenotype. Many modifier genes produce a different phenotype from their target mutation, and some produce no mutant phenotype at all when the mutant allele of the target gene is not present." (From Atherley, Girton and McDonald, The Science of Genetics. Saunders College Publishing, 1999. ISBN 0-03-029232-8.) When the mutant allele of the target gene is not present, the wild type allele of the target gene is present. So analysing the inheritance relationship of the mutant modifier gene to its wild type allele requires the presence of the mutant allele of the target gene to be present.

Also, there is a difference between WC (wild caught) and wild type (WT). Wild type (AKA normal) = 1) the most common phenotype in the wild population; 2) the most common allele of a given gene in the wild population. A wild caught creature probably has a wild type phenotype/genotype and was captured in the wild. A wild type creature can be a million generations captive bred as long as it has the wild type phenotype/genotype. Wild type at the modifier gene's locus is required. Wild type at every locus is usually helpful but not required. Wild caught is not required.

A couple of more definitions:
Allele = one of two or more versions of the same gene. Alleles have the same genetic locus. Two alleles can form a gene pair. Example: In the corn snake, the motley gene, the striped gene and the corresponding normal gene are alleles. And the amelanistic gene, the ultra gene and the corresponding normal gene are alleles. However, the amelanistic gene and the motley gene are not alleles because they do not have the same locus.
Locus (plural--loci) = A particular gene's location in the genome (chromosomes/DNA in a sperm or egg). Although there are exceptions, most genes keep the same locus over the generations.

Wild type is piecemeal in nature. A given corn snake may have two amelanistic alleles at the amelanistic locus and still have two wild type alleles at the anerythristic locus and at the caramel locus and at the motley locus.

You are saying that the halo mutant allele has a locus that is independent to the amelanistic and anerythristic genetic loci, Halo phenotype occurs when a halo allele is paired with the corresponding normal allele, and green blotched is produced when the gene pair has two halo alleles. Can green blotched be identified in amelanistic corns, or does it require snow to show up? What is commonest in snow corns--non halo, or halo/green blotched? If non halo, that is the wild type allele's phenotype. Once you assign the wild type phenotype, you just need numbers and breeding results to determine whether the halo allele is dominant/codominant/recessive to the wild type allele. Matings: non halo snow with at least one halo or green blotched parent x non halo snow with at least one halo or green blotched parent, halo snow x non halo snow, halo snow x halo snow, green blotched snow x green blotched snow, green blotched snow x halo snow, green blotched snow x non halo snow. Record total number of eggs, total number raised to age where non halo, halo or green blotched can be identified, number of non halo, halo and green blotched.
I understand the genetics and the terms, thanks
I have done the majority of those breedings already (http://www.cornsnakes.com/forums/sho...d.php?t=145967) - working toward the others, of course.
As for GB being in Amels - the issue is similar to it not being visible with melanin, the red pigment "covers" it. I have seen many amels with a more orangey tone to their saddles, but I don't know if I'd say that makes them green blotched.
It already takes 6-12 months to determine if a snake is a halo/green blotched WITHOUT dealing with other pigments (red and black), so as much as I can I'm sticking with the snows / blizzards (where the yellow shows up the best & at the youngest age).
 

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