# Roan Gene Explained on AFRMA.org



## Amtma Mousery (Jan 29, 2015)

Hello,

On the AFRMA website (linked below), it states that Roan recessive and Merle are separate genes- ro/ro and ro^un/ro^un. How is this accurate when Merle and Roan frequently simultaneously appear in the same litters?

Does this imply that it is not possible to breed Merle with Roan dominant gene?

http://www.afrma.org/geneticcodesmse.htm

What would be the resulting combination of Roan recessive X Seal Point Siamese?

I bred a Roan buck and 4 Siamese does. My resulting litters were all Roan. Does this imply that my Seal Point Siamese are homozygous carriers of Roan recessive gene, or I have the Roan dominant gene?


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## Amtma Mousery (Jan 29, 2015)

Hello,

So I thought I'd post a follow up about my question from recent research that I conducted to self-answer. The theorized Roan gene alleles displayed on AFRMA orginates from Virginia Pochmann personal experience and study. Thus, understanding that such description of the Roan gene is individualized and may not be accurate for all Roan.

Roan dominant, is described as Rn. This was distinguished and established by Jack L. Ball during his original experimentation with the Roan gene in 1986-1987.

Virginia Pochmann study is of more recent publication. Within her test group, she focuses upon and acknowledges the presence of Roan recessive- additionally stating that Roan recessive and Roan dominant do not at all appear similar phenotypically. Now, this leave the implication that she also had Roan dominant or at least seen it, but she fails to address this within her writing.

From her test group, she establishes the genetic difference between Roan recessive - ro/ro and Merle - ro^un/ro^un. Now, this is where I was confused... the Roan and Merle gene are not specifically separate identities. They are rather alleles that serve as a subjective place holder/reference to the gene that is causing a modification in a mouse's coat. Basically, she concludes that Roan and Merle are the same identity. But during development of the embryo, the gene is unstable and in result revert back and forth between itself causing the coat variation in Merle mice. She refers to the difference 'changes' as Roan - where the gene remains stable and is overall one pattern/color, or as Merle - where the gene becomes unstable and is multiple patterns/colors. Her identification of ro and ro^un do not have any objective value but are rather just identities that we can use to distinguish between the physical differences in Roan and Merle.

This definition manifest as such:
A Roan mouse is ro/ro because it has Roan fur.
A Merle mouse is ro^un/ro^un because it has Merle fur. ro^"un" stands for "unstable".
Both are the same gene, and can change randomly within the embryo- resulting in not ever breeding true.

What Virginia Pochmann does not specifically acknowledge is the dominance between Roan recessive and Roan unstable genes, which can be simplified to: What results for a mouse that is heterogeneous for ro and ro^un? Does the mouse acquire a Roan or Merle phenotype, or do the alleles mutate to homozygous of one or the other?

From a purely visual breeding standpoint, such question is hard to answer without actual scientific evaluation of the genes at work. In result, she concludes that "these mosaic animals should be of great interest to scientists. I hope someone in the field of genetics will come forward and let me give him or her some of these fascinating animals to work with."

I hope this description is useful. I have linked the two studies below.
http://www.afrma.org/roanmice.htm
http://www.afrma.org/roanmiceinh.htm

I personally am very interested and breed the Roan variety. I recently bred a Roan buck, ro/ro to 4 Seal Point Siamese. The resulting litters are a week old and all of the pups have black eyes. This raises questions of the dominance of the Roan gene. I will continue to post my findings and recent litters in the 'Breeding Plans' section.

For any UK breeders, do you guys have the Roan recessive gene there? I have not seen any pictures shown.


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## Lilly (Nov 21, 2015)

There used to be a dominant gene in the US but its all but died out, I think one breeder in isolation in WI still claims to have it but are waiting in someone to get hold of them and test breed to see if this is in fact the case.

If you are talking about roan now in the US then roan AND merle are ro^un

AFRMA is a good site but they have articles for decades on there and a lot of the info is now outdated. They barely do mice anymore with only one or two breeders left so the mouse info is very old.

Basically ro^un = unstable roan, unstable in that the amount of roaning is very variable, from none at all in some patches (so merle) to very roaned making a black roan appear pale grey from a distance.

It is possible that the same gene might change to unstable or not in the embryo and that roan mice are ro/ro but it is still recessive to non roan/merle, so breeding roan to siamese will result in black mice (unless the roan carries siamese, in which case black and siamese mice) but they will not be roan themselves, they will carry it.

I will ask around though and see if breeders have got merle from a roan x roan pairing, because that would prove its either so unstable it can be either ro or ro^un in the embryo or that it is in fact the same gene and other modifiers are at play


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## Frizzle (Oct 6, 2011)

Lilly summarized it well.

In breeding two merles together, you can anything from roans to "phantom" merles (genetically merle, but with no roaning, I've only had it happen a couple times).

If you're looking for how to identify if your offspring are merle, check the bellies. On dark pigment, you'll be able to see the pattern sooner. If you have "early" merles and dark pigment, you'll be able to see if there is a top patten around day 3-5. Early merles will have an identifiable patten from fur up, though as the mouse matures the pattern cleans up some. In my experience, these merles end up with lighter roaning. A late merle is one that does not show a top patten until it begins to get is adult coat. It will undergo a rapid change, and seemingly overnight (really over about a week) you will be amazed by what they will look like.

I currently have both in my merle population, though I'm trying to phase them all into early merles, as this is more desirable from an early selection standpoint, as well as there is more leeway for U8 showing.


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## Amtma Mousery (Jan 29, 2015)

I acquire Merles from Roan x Roan.

It is theorized that Merle and Roan are the same gene... ro^un with multiple k-factors influencing the shading and ticking. In result, regardless of Merle x Merle, Roan x Roan, or Merle x Roan- in regards to my Roans/Merles, I get a random mixture. The gene will never breed true.

I bred Siamese does x Roan buck = Black, Merle, Roan, and Siamese

I have early Roan and Merle that I have been breeding for over 6 years. My original stock originates from Animal Exchange, MD, which originates from Fredricksburg Mousery.


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