Roan

I consider it a white pattern because it adds white and is a kit gene mutation.

But so does Grey?

Gray doesn't so much as add white as take away color. I have seen it argued both ways for roan. UC Davis says "Roan is a white patterning coat color".

Roan isn't caused by an absence of melanocytes though, as the colour can come back and varies with the season.

[quote]Roan isn't caused by an absence of melanocytes though[/quote] are you sure? Roan is thought to be a kit gene mutation.

It doesn't vary with season so much as only affect the shorter hair on the coat. If you part a roans winter coat the white hairs are plainly visible.

^ What [b]admin[/b] said. Classic roan is still there but varying hair length makes it appear gone. Some horses have the opposite, having their roan hairs get more pronounced in the winter.

I've heard roan and rabicano being classified as "mixed white" patterns, due to appearance alone. Even dominant white is also a KIT mutation and can cause variable roaning with the pinto that can remove pigment with age like the Franches Montagnes examples in one of the studies.

Even LP can vary pigment and lack of pigment with age or gain pigment back if a stallion's testosterone levels drop. Most of it goes to "rules not really being rules" and just human classifications that nature doesn't like to always follow.

I'm torn now- this is supposed to be a "Colour 101" type article- should I leave Roan in with the modifiers, with an explanation, or completely confuse everyone and put it in with the "White patterns" ?

I would add it into the white patterns. You can always add something to this effect: "some have considered roan a modifier but recent genetic developments have lead us to believe that it should be classified as a white pattern." Then if someone asks about it you can explain that it is a kit gene mutation and its similarities to dominant white and sabino roaning.

I think most will be fine with that. There will probably be quite a few in the audience who have always considered roan a white pattern.

Oh NO there won't, trust me!! These are Mini people and their eyes glaze over when you try to explain that Silver does NOT show on Red, however much they think it does, and "cream " Dun is not actually a colour if it does not contain Cream. I am going to lose them at " there are only two colours, Red and Black" I know we have quite a few educated Mini people on here- and I KNOW they will know what I am talking about!! This is an attempt to get colours correctly identified on registration papers.....

My biology book classed roan as a mixed pattern when presenting Mendelian genetics. But the way they were presenting it, I'm pretty positive the book was wrong.

Best of luck with the presentation rabbitsfizz. Especially with that audience. If you have anyone videotaping it I would love to see you spreading color genetics education. ^_^

JNF I came across this infamous chart awhile ago and it makes many a color enthusiast's s brain hurt.
http://i872.photobucket.com/albums/ab28…

My brain hurts and I haven't started!
Luckily I am not giving it live, it is written, giving me time to pack my bags and get out of the country!!
I am chanting "KISSKISSKISS" to myself, all the time....

You can do it! With all those smilies we don't have a cheerleader? I guess this will have to do :toast :toast :toast