[ryu2832]

Originally Posted by JBandRio

is that we have seen many Splash horses that are not Tobi that have the white coming up from the belly and "pouring" out into the topside of the horse, and I am now making a connection between that, and Tobi horses who have the same type of pattern (which is not a typical-looking Tobi pattern), and am wondering now if Splash is manipulating, or perhaps overriding, how the white placement appears.

It's a pretty strong theory that Frame pushes white off, or at least down, the leg, so it wouldn't be a big stretch to think that Splash could manipulate the presentation of white on the body.

It basically a question of what gets turned on when.

All cells destined to become pigment producing cells (melanocytes) migrate from the edges of neural crest tissue (what is destined to become the spinal cord).

If you accept that 'white' in patterned horses is caused by the absence of pigment producing cells, and that the location of pigment producing cells is determined during development, you can make some inferences about what gene(s) are turned on when.

We know that early migrating melanocytes migrate medially, and that late migrating melanocytes migrate dorsally. So if you look at a pattern like Frame, there is medial white with dorsal,ventral pigment. So you could infer that the gene(s) responsible for this pattern are early in migration, and that late migrating cells are not affected.

I think if you follow the early-medial, late dorsal you guys could probably rank when/what pattern genes are 'on' (because I have no idea what pattern is which ). Like (Early) Frame>Overo>Tobiano>Sabino (Late). I have no idea if that is correct.

Just remember that white is absence of melanocytes, and that cell death can be early or late. The only rule is once it's white, it's white--no takebacks! (Spotting on white is a whole different thing.) Have fun!

[JBandRio]

Oh Gawd, I'm not sure whether to be glad I've already had a glass of wine, mad that I have, or mad that I haven't had two!

I think I totally get what you are saying, but will have to revisit in the morning when I've had a hopefully better night's sleep than I've been having

[accphotography]

Originally Posted by JBandRio

Oh Gawd, I'm not sure whether to be glad I've already had a glass of wine, mad that I have, or mad that I haven't had two!

I think I totally get what you are saying, but will have to revisit in the morning when I've had a hopefully better night's sleep than I've been having

I'll second that... and I haven't had a drink. I will re-read in the morning as well.

ACC

[JBandRio]

Ok, I've digested this again and understand the specific example of Frame (which also seems to point back to what I still believe in that a Frame-only won't have white crossing the centerline ). But I need to write some things down on paper, with this new information, and see if I can make other patterns make some sense with this, and then finally, see if I can make the theory of Splash overriding the placement of white that Tobi might prefer to have.

We already know there is a dominance order when it comes to Agouti - Bay over Brown over black (don't remember where wild bay falls, my guess is it's bay-wild bay-brown-black), so this now makes me wonder if something similar is going on here, just on different locations. Or even maybe we're looking at fewer locations than we think, but other factors that determine which expression we see?

Geeze, maybe I need a glass of wine for breakfast

[ryu2832]

I thought I really watered it down almost to the point where I was pretty uncomfortable.....

But if this the the neural tube(spine):

XXXXXXXXXXXXXXXXX

Eary pigment cells move:

XXXXXXXXXXXXXXXXX
P P P P
P P P P
P P P P

Late Pigment cells move:

XXXXXXXXXXXXXXXXX
<----P----->

There are a couple other factors that tell pigment cells where and when they can move. Certain types of other developing cells form barriers, the two most well known are the ends of the neural tube (primative head and tail).

Somites are another barrier to cell migration, they begin along the edge of the neural tube (where the ribs will be) and migrate medially (like the finished ribcage). They are also responsible for the formation of the skin on the back (so a pattern with no white crossing the back, is probably happening during that time of development, late.)

[ryu2832]

Originally Posted by JBandRio

Ok, I've digested this again and understand the specific example of Frame (which also seems to point back to what I still believe in that a Frame-only won't have white crossing the centerline ). But I need to write some things down on paper, with this new information, and see if I can make other patterns make some sense with this, and then finally, see if I can make the theory of Splash overriding the placement of white that Tobi might prefer to have.

We already know there is a dominance order when it comes to Agouti - Bay over Brown over black (don't remember where wild bay falls, my guess is it's bay-wild bay-brown-black), so this now makes me wonder if something similar is going on here, just on different locations. Or even maybe we're looking at fewer locations than we think, but other factors that determine which expression we see?

Geeze, maybe I need a glass of wine for breakfast

Yes, Perfect! Awesome!

I did a little more digging and added some information on patterns that cross the back.

[RiddleMeThis]

I think I get it lol

[accphotography]

Me too... but how about that glass of wine anyway. LOL!

No, really. I'm with JB that I need to sit down and draw some of this out and see what I can come up with.

Ryu... maybe I missed it but do you have anything that would say/show how one pattern would influence another despite being at different development times?

ACC

[Haas Horse Farm]

My understanding on the Agouti placement is:
wild bay A+
bay A
brown At
black a

I also thought that there was a particular breed of pony that had white barrel markings like the black and white Hampshire and Saddleback pigs do...

[JBandRio]

HHF, so you're saying that Wild Bay dominates over Bay? I can't see how, or else Wild Bay would be more prevalent than regular bay, I would think.

That said, I could see how the wild bay got bred out and the next most dominant variation is now the most common.