Just discovered something today! Feeling Stupid :(

Markus Jayne · 03-09-05, 06:51 AM

I am building a new genetics page on my site. It will be visual and interactive. I finished the recessive and co-dom pages and I was about to do one for double-co-doms and I wasn't sure what the outcome would be. I have a Pewter which is a combination of two morphs, pastel jungle and cinnamon. The bumble bee would be considered the same type of double morph and I think the only other double co-dom.

I started to figure out the percentages of offspring and I surprised myself. I wasn't sure so I called Colette at the Snake Keeper who always loves talking about genetics. She confirmed that by breeding a Pewter to a normal, I have a 25% chance of producing a Pewter, Paste Jungle, Cinnamon and Normal.

It surprised the heck out of me and I guess I just never gave it much thought.

Needless to say it made my day!

Did everyone else know this or am I the only one that feels a little dumb right now?

Mark

Bristen · 03-09-05, 07:15 AM

LOL! I thought the big question was Bumble Bee x Pewter, that would of been a little more complicated.. Pewter to normal is an easy one, just like Bumble Bee to normal... Bumble Bee to normal is 25% normal, 25% spider, 25% pastel and 25% Bumble Bee... Genetics is a big part of the fun in my opinion!

So what are the plans for the pewter? I'm assuming you have multiple female pastels ready for him? a super-pastel pewter maybe in the works?

Have a good season and flood us with pictures please :-)

Bristen.

MarcB · 03-09-05, 07:43 AM

Mark, I can honestly see how the outcome from such a pairing can be somewhat overlooked! Thats what makes working with genetics so fun!

Now imagine crossing your pewter to a an homo double recessive mutation! Ouch...

RandyRemington · 03-09-05, 08:41 AM

You're probably right but it MIGHT get a little more complicated.

With bumblebee we have reason to believe that pastel and spider are different mutations of different genes that don't even happen to be on the same chromosome. This is because the killer bee was created quickly.

With pewter, we don't really know much yet. What if it turns out that cinnamon and pastel are different mutations of the SAME gene? It isn't possible to have more than two copies of the same gene (one from mom and one from dad) so if they are alleles then you could never produce a cinnamon super pastel or a pastel supper cinnamon much less a super pastel super cinnamon. Under this scenario pewter X normal would produce 50% pastel and 50% cinnamon but no normals or pewters.

It's also possible that any two mutations you are combining might just happen to be on the same chromosome. There are only so many chromosomes (I can never remember how many for snakes, probably in the 20's) so with as many mutations as we have we are bound to run into some that just by chance are located on the same chromosome. Depending on how close together they are it might be very difficult to get a crossover to happen in-between them to allow a copy of the common chromosome to be created by a double het with both mutations. If pastel and cinnamon are different mutations of DIFFERENT genes that just happen to be close together on the same chromosome you will also likely get 50% pastel and 50% cinnamon with no pewter or normal from breeding pewter X normal but the difference is that eventually you should also get a very few pewters and normals. If you ever did get that rare pewter from pewter X normal you would know that it had the crossover and would be different from the original pewters from pastel X cinnamon and would be an important first step to producing super pastel super cinnamon.

Of course it may well turn out that cinnamon and pastel are completely unrelated mutations of different genes on different chromosomes and you will get the 25% split of each normal, pewter, pastel, and cinnamon as expected but let us know. The unexpected synergy between pastel and cinnamon to make pewter has me wondering if they aren't related in some way so the results might be very interesting and surprising to many.

Markus Jayne · 03-09-05, 09:01 AM

My thought exactly Randy! Well...not really except for the part that pastels and cinnamons are the same in a way.

Randy, you are by far the 'go to' guy when it comes to genetics and I was hoping you would jump in on this one.

In my discussion with Colette I stated that it will be interesting to see what the leucy that was produced from a Lesser X Mojave cross will produce. I'm not saying that Lessers are a different shade of Mojave but they are far more similar than a Pastel and Cinnamon.

I have a very good chance of proving the Pewter out this year as does Greg. I'll certainly keep you posted.

Mark

Scales Zoo · 03-09-05, 09:11 AM

That is more of a statistic question, a lot of people don't seem to "get their head around that"

Each co dom has a 50% chance of passing it's one copy of the gene, but those 50% overlap to give you 25%, 25%, 25%, 25%.

It is really exciting dealing with the horses (90% of color and coat patterns are co-dominant) because very few horse people even have a sniff about inheritability - and having a stud that has 75% chance of throwing color (3 different combinations of) is valued the same as a brown horse in many cases (in Canada anyways).

Male double co-doms, especially if one happens to be homozygous, is just invaluable as a breeder male, be it snakes or horses, IMO - and definitely something to hold back.

A "super pewter" that was homozygous for pastel, and heterozygous for cinniman, should throw 50% pastels, and 50% pewters, bred to normal females. Put a value on that male!

Ryan

atw · 03-09-05, 03:50 PM

I think an easy way to explain double co-dom breeding is too think of a double co-dom as a visible double het. Using this as an example:

http://www.ralphdavisreptiles.com/ma...owxdh_snow.asp

Replace 'Albino' with 'Pastel', 'Anerythristic' with 'Cinamon' and 'Snow' with 'Pewter'

Therefore, if you breed your 'double het' pewter to another 'double het' pewter you would get:

* 1 Normal
* 2 Het Cinnamon
* 2 Het Pastel
* 4 Double Het for Pewter
* 2 Pastel Het for Pewter
* 2 Cinnamon Het for Pewter
* 1 Pastel
* 1 Cinnamon
* 1 Pewter

Now, what is a 'het cinnamon'? A cinammon. What is a 'het pastel'? A pastel. So...

* 1 Normal
* 2 Cinnamon
* 2 Pastel
* 4 Double Het for Pewter
* 2 Pastel Het for Pewter
* 2 Cinnamon Het for Pewter
* 1 Pastel
* 1 Cinnamon
* 1 Pewter

What is a 'Pastel Het for Pewter'? A pewter. And a 'Cinammon Het for Pewter'? A pewter. So...

* 1 Normal
* 2 Cinnamon
* 2 Pastel
* 4 Double Het for Pewter
* 2 Pewter
* 2 Pewter
* 1 Pastel
* 1 Cinnamon
* 1 Pewter

Now... what is the difference between a 'Double het for Pewter' and the original bottom 'Pewter'? This is where I get confused. If the first scenario Randy described is true, a 'Double het for Pewter' and the original, 1/16 Pewter would just be Pewters. If, however, the second situation is true, I think the double hets would be pewters and the 1/16 Pewter would be 'Super Pewter Super Cinnamon' (assuming that it has already been proven that there do exist 'Super Cinnamons').

Randy,

What do you think?

Adam

Scales Zoo · 03-09-05, 06:47 PM

Pewter means it is het for pastel jungle and cinnamon, which are co-dominant traits. He's breeding it to a normal. If it was just a pastel jungle (het) he'd get 50% hets from that breeding to a normal. The hets are pastel jungles, super pastel jungles are the homozygous form. It is het for both cinniman and pastel and being bred to a normal.

Your above numbers are correct for recessives, but where you have pewters, those would actually be super pewters (homozygous for pastel and cinnamon), because it is co-dominant genetics. Same as where you have pastels and cinnamons, those would be supers - as the hets are pastels and cinnamons.

I doubt anyone has ever made a super pewter - but I know it would be damn expensive, and for good reason.

Ryan

RandyRemington · 03-09-05, 11:07 PM

The scenario where cinnamon and pastel might be alleles is hard to give an example for because we are only just starting to get into snake genetics.

Anyone work with motley and striped corn snakes? Those are recessive mutations that are alleles (actually they are so mixed together now days that some would argue they are the exact same mutation - but at least originally they had distinct looks). The double het motley stripe is actually a mutant because both mutations are the same gene so the double het doesn't have a normal copy of that gene. It's still not a good example because the single hets are normal looking since it’s recessive and not co-dominant.

If cinnamon and pastel end up being alleles (two different mutations of the SAME gene) then the pewter doesn't have a normal copy of that gene to give to any of it's offspring. About half of it's babies with a normal will get the pastel copy and the other half the cinnamon copy. Since it can only give one copy of a given gene to each baby it will not be able to produce a pewter when bred to a normal. It would also not be able to produce a normal since as stated already, it doesn’t have a normal copy of the common cinnamon/pastel gene.

The linked gene scenario where both mutations are different genes BUT on the same chromosome is also hard to explain and hard to find a good example of. I think there is an example in black rat snakes that someone pointed out once and perhaps also in leopard geckos and even perhaps Burmese pythons (green and labyrinth).

I suppose the most likely scenario is still that they are different mutations of distant genes and you will get the four way 25% chance split as expected. If it comes out one of the other two ways I'll try to do a better job of explaining why. Hopefully both you and Greg will have several clutches so we will get a nice big sample size and have it pretty much nailed down right off the bat (either you will get some pewters and normals or you won’t, with the linked scenario it might be that you only get a very few and not the expected 25% pewter and 25% normal).

Anybody remember the gender of the ebony (yb + granite) or know if it could possibly produce this year? That is another one I'm anxiously awaiting results on.

I'm pretty much expecting that lesser, phantom, and Mojave are all at least alleles if not the exact same mutation (perhaps with other genes causing the differences in lines) so I think that is perhaps the best example even though it also hasn’t been tested yet. I would expect the phantom X lesser produced leucistics when bred to a normal to produce about 50% lessers and 50% phantoms with no normals or leucistics. The question of alleles vs. other genes making the difference might be answered by how neatly the babies fall into the two categories or if there is a continuum between the two types. Pewter and Ebony seem a little trickier but might well go the same way with all of their babies X normal being mutants but none being pewter or ebony.

The super pewter and ebony might just not be possible.

Bristen · 03-10-05, 09:28 AM

wow, I thought it was rather simple discussion when Mark first posted, but I guess that I'm the one that's "dumb" here hehe...

What I don't understand Randy, is what makes you think that pastel and cinnamon are alleles (two different mutations of the same gene) more than others? I'm assuming you are thinking that because they are similar in appearance? Like the mojave/lesser/phantom/platinum?

I don't understand a whole lot of genetics, but I always thought that there were so many possible combinations that having two different morphs that are alleles would of been rather slim? I suppose with the amount of morphs out there now you would think we would definately be hitting those odds... Have we proven such a case to exist yet in Ball Pythons?

Thanks for the great input Randy, as always you are very interesting to read!

Bristen.

RandyRemington · 03-10-05, 09:51 PM

Multiple mutant alleles are fairly common in species with better studied genetics. We have only just barely begun to cross snake morphs and the few possible allele situations we have come across so far don't seem to get well studied (I can find almost no information on the green and labyrinth burm crosses that have been available for like 13 years or so).

My guess that pastel and cinnamon MIGHT be alleles is mostly based on them having so much in common. I think Graziani originally coined "cinnamon pastel" based on the similarities and that's probably also why he decided to make the cross. Also I think pewter looking so extreme and like more than you would expect just from the combination tends to support something going on here. Of course only time will tell but we shouldn't have to wait too many more months now!

Bristen · 03-11-05, 07:08 AM

interesting stuff.. I almost hope they are not alleles because that would mean we could have more combinations heh :-)

yup, you are right... 2005 is going to be an interesting year because, most likely, we will be seeing a LOT of crosses and breeding results that will help clear up some genetic stuff... one of the things I can't wait to see is Ralph Davis' lucy x normal breedings to see what the offspring will be...

Thanks,
Bristen.