# Merle meeces-what's up with them?



## moustress (Sep 25, 2009)

There seems to be no consensus, in the sources I've looked at, as to just how the genetics of merles works, what kind of coats you might get out of breeding two of them, or how to move between pied merle, merle, and roan.

I'd like to hear from anyone on the subject. What you know, what you've experienced, what you've seen...and what you've read complete with references if possible.

Me; I'm just that kind of person who wants to KNOW! The mousies that turned up in litters from my extracting the necessary recessives to remake my fawns included about a half a dozen that look roan and merle, and I have one litter, and I'm expecting another litter any day, I hope (unless she's just fat!).

Can anybody help me find a clue? :?:

Fifteen minutes later: Impatience can be a virtue! I Googled for merle mice and got a link to a couple of articles in the AFRMA site. A couple of their members worked extensively with merles and roans; it appears that a merle is a roan that is also homozygous
in the recessive p, but with a twist. the p^un, an unstable gene that cause pink eyes and also causes patches of roan fur to revert to fully pigmented. I am therefore convinced that not only is this a mosaic phenomenon, possibly transgenic, and that my
merle and roan looking meeces ARE caused by the splashed gene as I have described it, being a transgenic element according to the work that I have done. I bet that my odd eyes are also an example of this. It all fits together very neatly.

Could it be that the appearance of roan/merle in a mousery in 1986 was the first appearance of splashed/tricolor mousies? Was it a really a spontaneous mutation or did Bob have a splashed mousie in the wood pile!? Or are they just similar and unrelated phenomena?

I love questions like these! They tickle my breeders fancy and spurs me on to breed for the sake of investigation in hopes of learning more about what going on.


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## Alex (Jan 29, 2012)

I came across a book on google "The Colors of Mice: A Model Genetic Network". Have you read it?


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## Stina (Sep 24, 2010)

In my experience with merle, and I have bred it, it is simple recessive and the reversion to solid patches is random. Those with heavier markings are slightly more likely to produce more with heavier markings and those that are roan-like are slightly more likely to produce more roan-like markings.

Mosiacism is NOT genetic....so it would be impossible for most merles to be mosiacs since they readily reproduce the markings.

I don't see how p would have anything to do with merle since merles can be ANY color whatsoever....besides white...nor do I see how it could be caused by splashed, since merle can be combined with it or appear in lines with no splashed history whatsoever. That's not to say a splashed can't *look* merle...but from my experiences, I do not believe merle is in any way associated with p or Spl.


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## moustress (Sep 25, 2009)

I was talking about p^un, which is not the same as p. The unstable nature causes some of the colored patches to do things like create roan/merle. Apparently the unstable gene and and it's partner do not work together, but separately do their own thing, which is why it's called mosaicism.

Since it hasn't been explained where roan/merle came from, any speculation is just that: speculation. Since the p locus is on the same area of the gene as the other color and marking genes, I think it's not unwarranted to wonder about it in relation to the tricolors, as I still harbor the belief that tricolors are a transgenic phenomenon. Anything that alters the outcome of color and marking genes by causing novel expressions of color and markings such as splashing and tricoloring could be related or at least act in a similar fashion.

Here are some pix from a few years ago:

Here some pictures of my F3 generation of brindle/tri crosses, from which I got a lot of interesting marked mice.







Here are pix from a few years ago of some mousies from brindle tri litter:


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## Autumn2005 (Apr 21, 2010)

So mice who are p^un can be p^un/p^un but still have black eyes?


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## moustress (Sep 25, 2009)

Hmmm...I'm not sure about that...it sounds plausible, since the gene causes random reversions.And/or maybe it's responsible for odd eyes...another good question.


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## Stina (Sep 24, 2010)

None of those mice look merle/roan to me.....just poorly marked pieds with uneven edgess...

Also, in my experience it doesn't show any linkage type effects with any of the other color/marking genes (and eye color corresponds to genetic color...a black merle has black eyes and I have never seen a merle odd eye). If it was on the p locus, then then it wouldn't behave the way it does...which is as a simple recessive, with either p/p or any of the c-dilutes, or any other color. P/p^u would not be merle...as such p^u/p^u would be merle and/or roan.....not just roan. It would also have to be codominant with p, since pink eyed merles exist... but they aren't produced in any higher a ratio than with any other color...so it can't be the same locus....nor does it behave as though it is linked with any color, as ratios seem to trend to normal simple mendelian genetics as a simple recessive gene with ANY other color or marking. If it were on the p locus it would not behave as a simple recessive with p or any of the c-dilutes.

Like I said, mosiacism is IMPOSSIBLE as an explanation for a trait that behaves as a simple recessive..... Mosiacs are animals the the genetics of 2 individual animals in one body...they canNOT reproduce any traits caused by the mosiacism. It sounds like you are trying to describe something completely different from mosiacism....but I do not understand what... All I know is that merle is NOT explained by mosiacism.

I just read the article from AFRMA that mentions p^un and it does NOT say that merle is caused by this gene.....she COMPARES merle to it, and then proposes a possible gene of ro^un. Nowhere in that article is it suggested that merle is caused by a gene on the p locus. The article also uses an incorrect definition of mosiac. ...for example, a tortoiseshell or calico cat will have different gene expressions at different colored markings, and their markings often have midline edges...but they are not called mosiacs. Pied animals will also have different gene expressions at different markings, but again, they are not called mosiacs. Also, the article is simply a suggestion of a possible cause for merle...however since it acts as a simple recessive I don't believe the article is likely correct....it was also written in 1988 and is very outdated.

There are many genes that cause irregular markings...such as merle in any species, any brindle in any species, splashed mice, pied animals of any species.........the variations are not usually explained by an unstable gene....often just modifiers of the gene and variations in expression as the embryos develop.

There is a known, studied, dominant roan gene (Ro) in lab mice...just b/c that exists, does not mean that the recessive merle we have in the pet fancy is in any way related to it.


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## moustress (Sep 25, 2009)

Which pictures are you referring to, Stina? The ones in this post? Those clearly have white hairs interspersed with the agouti to varying extent over many of the colored area, along with patches of sold hue.


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## Stina (Sep 24, 2010)

your F3 generation of brindle/tri cross photos. I see some white intermixed hairs...but it doesn't really look like merle to me on those mice...it looks like really bad uneven edges to the white markings. I could be wrong and it might be merle...but even if it is, I don't think it has anything to do with the splash gene...it was probably just a hidden recessive you didn't know was there till then.


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## moustress (Sep 25, 2009)

These mousies are the reason I think my younger individuals with this kind of mixing is not really merle (or roan) but an aritfact created by the splashed gene. It seems to me that brindling, with the dilutions, plus the splashed gene, uields this kind of coat.that's why I'm having a couple of litters off of my younger meeces, to see what the distibution of color is like. If it is merle/roan, it should give me a approximate percentage of different kinds of coats, some looking like pied merle, some just pied, and some regular merle IF
the markings are recessive, probably not regular merle if the markings are dominant. If I get some tricolors, some typical splashed, and some that look like the parents, I can be pretty sure that the parents are splashed, not merle or pied merle, or pied roan.


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