Linked genes...

Have any linked traits been found in corn snakes yet?

Corn snakes have 36 chromosomes (i.e. 18 different chromosomes) and at least 12 different known colour mutations so we can't be far off (if we're not already there) of having 2 mutations in the same chromosome.

Has anyone looked into this, and if not then why? It probably wouldn't be that hard for some of the big breeders who might be breeding the same pair over many years to have a go at .

I don't think any have been unequivocally established, but I suspect people will be looking at that with pied and diffusion. But first, I think there might be a little work left to be done on pied.

desertanimal said:

I don't think any have been unequivocally established, but I suspect people will be looking at that with pied and diffusion. But first, I think there might be a little work left to be done on pied.

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pied? There is a pied gene in corns :eek1: ?

I don't know a ton about it, but there are some corns with pied markings, and people are working on seeing what the genetic basis for it is. I haven't gotten the impression that it's at all worked out yet. I'd guess there'd be something about it in the 2007 cornsnake morph guide.

It's often referred to as pied-sided. The markings usually aren't very large, like as seen in ball pythons, and it occurs in the diffusion along the sides. Here are a few links to see some photos:
http://www.cornsnakes.com/forums/showthread.php?t=47722&highlight=pied-sided
http://www.cornsnakes.com/forums/showthread.php?t=47789&highlight=pied-sided
http://www.cornsnakes.com/forums/showthread.php?t=40997
http://www.cornsnakes.com/forums/showthread.php?t=41697&highlight=pied-sided
http://www.cornsnakes.com/forums/showthread.php?t=23120&highlight=pied-sided

The last link is a really good one.

Intravenous said:

Have any linked traits been found in corn snakes yet?

Corn snakes have 36 chromosomes (i.e. 18 different chromosomes) and at least 12 different known colour mutations so we can't be far off (if we're not already there) of having 2 mutations in the same chromosome.

Has anyone looked into this, and if not then why? It probably wouldn't be that hard for some of the big breeders who might be breeding the same pair over many years to have a go at .

Click to expand...

As far as I know, nobody has identified any linked genes.

Even if two gene locations are on the same chromosome, they have to be fairly close together to have the recombination rate affected.

In my opinion, the big breeders do not do this sort of thing for several reasons. It takes a combination of genetics and statistical knowhow that most lack, as far as I know. And they need to maximize return for minimal effort. That means they don't have much time to spend on this sort of thing. And it means breeding double homozygous individuals together. While for linkage studies, you have to breed double heterozygous individuals to double homozygous individuals. You also need to know whether the genes in the double heterozygous individual are linked like so:

--A----B------
--a----b------

or like so:

--A----b------
--a----B------

Linkage studies require good sized numbers of babies for statistical analysis, too. One clutch of eggs won't cut it.

Yeah, I guess its not really economical for a big breeder to do.They're obviously just not big enough nerds like me to be bothered wasting the time :grin01: .

paulh said:

You also need to know whether the genes in the double heterozygous individual are linked like so:

--A----B------
--a----b------

or like so:

--A----b------
--a----B------

Linkage studies require good sized numbers of babies for statistical analysis, too. One clutch of eggs won't cut it.

Click to expand...

You don't actually need to know which way round they are linked to work it out because you are using a double homozygous individual therefore you know that one of the parents is:

--a----b------
--a----b------

and you can therefore eliminate all of this parents contribution to the offspring to work out how the alleles are linked in the other parent (assuming there is linkage).

If there is linkage then the actual offspring will be very different from the expected offspring and the two highest progeny groups will give you the parental types. If there is no linkage then the actual osspring should be pretty close to the expected.

One egg batch will not be enough...but say you bred the same pair of corns together throughout their life then youd tally up quite a lot of babies.

^ *offspring

Typo

Intravenous said:

If there is linkage then the actual offspring will be very different from the expected offspring and the two highest progeny groups will give you the parental types. If there is no linkage then the actual offspring should be pretty close to the expected.

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Knowing the double heterozygote's genotype for sure is most useful when two loci are weakly linked.

Intravenous said:

One egg batch will not be enough...but say you bred the same pair of corns together throughout their life then youd tally up quite a lot of babies.

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Yeah, that's why us nerdy hobbyists are most likely to gather the data. :cheers:

desertanimal said:

I don't think any have been unequivocally established, but I suspect people will be looking at that with pied and diffusion. But first, I think there might be a little work left to be done on pied.

Click to expand...

Pied-sided may only occur in bloodreds, but that doesn't mean they are gentically links as the poster means in this thread. That's anotherstpry, yet, and I don't see a point even guessing at the inheritance of pied-sided in non-bloodreds until more data is avaialble.

BUT, back to linked genes....

Sure, you are correct, but genes aren't necessarily linked just because they are on the same chromosome. Rememer that, due to crossovers, the further apart 2 loci are one the same chromosome, the less linked they will appear. Ones far apart are inhereted according to Mendel's rules of segregation and independant assortment. In other words, they aren't linked. Loci on opposite ends of the centromere are considered NOT linked for all practical purposes. SO, we might not be that close to linked genes after all.

I used to think that the lack of yellow in Charcoals (whether due to one gene or many working together) was linked to the charcoal gene, but not THAT close together on the chromosome. So, cross-overs DID occasionally occur resulting in charcoals with and without yellow, but that would have meant that we'd be able to get NON-charcoals without yellow. Since there is no real good evidence of that, I think my old hypothesis is pure bunk. LOL.

KJ

desertanimal said:

I don't think any have been unequivocally established, but I suspect people will be looking at that with pied and diffusion. But first, I think there might be a little work left to be done on pied.

Click to expand...

Pied-sided may only occur in bloodreds, but that doesn't mean they are gentically links as the poster means in this thread. That's another story, yet, and I don't see a point even guessing at the inheritance of pied-sided in non-bloodreds until more data is available.

BUT, back to linked genes....

Sure, you are correct, but genes aren't necessarily linked just because they are on the same chromosome. Remember that, due to crossovers, the further apart 2 loci are one the same chromosome, the less linked they will appear. Ones far apart are inherited according to Mendel's rules of segregation and independent assortment. In other words, they aren't linked. Loci on opposite ends of the centromere are considered NOT linked for all practical purposes. SO, we might not be that close to linked genes after all.

I used to think that the lack of yellow in Charcoals (whether due to one gene or many working together) was linked to the charcoal gene, but not THAT close together on the chromosome. So, cross-overs DID occasionally occur resulting in charcoals with and without yellow, but that would have meant that we'd be able to get NON-charcoals without yellow. Since there is no real good evidence of that, I think my old hypothesis is pure bunk. LOL.

KJ

KJUN said:

Sure, you are correct, but genes aren't necessarily linked just because they are on the same chromosome. Remember that, due to crossovers, the further apart 2 loci are one the same chromosome, the less linked they will appear. Ones far apart are inherited according to Mendel's rules of segregation and independent assortment. In other words, they aren't linked. Loci on opposite ends of the centromere are considered NOT linked for all practical purposes. SO, we might not be that close to linked genes after all.
KJ

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The term "linked genes" just means they are on the same chromosome (like two links in a chain) but yeah, if they're far apart enough they wont show any linkage...they're still linked as such, but you wont have any evidence of it.

Your charcoal idea sounds interesting...if the mutation originated in a charcoal line and they were very close together it could be possible.

I'll have to think up a project for myself .

If you want to try a linkage problem, then you can pick any two mutants because as far as I know the field hasn't been touched. For example, charcoal and motley or caramel and amelanistic. Even amelanistic and anerythristic. Good luck.

Intravenous said:

The term "linked genes" just means they are on the same chromosome (like two links in a chain) but yeah, if they're far apart enough they wont show any linkage...they're still linked as such, but you wont have any evidence of it.

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Yes and no. "Linked" is typically "accepted" to refer to genes that are independantly assorted.

I also think that no one is looking into linked genes is because there isn't really any incentive to. Corns have no economic interest (on a large scale to make funding the study of the genetics of them worthwhile) and are not a model organism. That makes dumping money into genetic studies essentially a black hole that would be nothing more than academic.