# Understanding Mouse Genetics



## KazzysKritters

I've been trying to research mouse genetics, to help with breeding once I get into fancy mice. I've been keeping and breeding reptiles the majority of my life, so I have a good understand of dominant, recessive, and co-dominant. Mice genetics seems to be a bit more complicated than I expected. I can't seem to find a good source to fully explain which genes are dom, rec, or co-dom. Could anyone point me towards a good resource for understanding the basics of the genes?

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## Lilly

I'm not sure how it is with reptiles but there's not really a list per se of all the dominant or recessive genes so the usual way is really to look up a color you are interested in and learn what makes it up and over time read about more and more colors

http://www.hiiret.fi/eng/breeding/?pg=4&sub=13

Thats a great site although gets a little messy right at the end, and covers most colors although there are some that are missing there.


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## KazzysKritters

Thanks! I'll check it out. With reptiles, everything is explained as either dominant, recessive, or co-dom. Everything I've seen with mice is all described in code. It's definitely unusual for me lol!

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## Lilly

Its the same with a lot of genetics really, genes are given codes and if the letters are capital its dominant, and lower case is recessive,

So

A = Agouti, dominant
a = black, recessive

d = blue dilution (so therefore a blue mouse if combined with black, or blue agouti if on agouti etc) recessive
D = undiluted

b = chocolate - dominant

e = recessive yellow - recessive

Re = Rex - dominant

go = angora - recessive

Avy = american brindle - dpminant

and lots lots more


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## KazzysKritters

From what I'm understanding, I have an Agouti, 2 blacks, and a REW (albino).

My male Black 









Female Black









Female REW









Female Agouti (she's not a fan of handling at ALL)









Nothing fancy (they were bought to breed for feeders). The female black and female Agouti recently had litters (and are both caring for both litters very well), the REW had a litter a few weeks ago but those babies are gone (buddy has baby snakes that needing some pinkies). If I'm understanding correctly, this will be the outcome of the current litters:

Black female-
All Black (a/a) babies

Agouti female-
50% Agouti (A/a)
50% ??? (a/*)

The * is confusing to me. Not sure what that means? I'm guessing the REW X Black would produce all black babies carrying (recessive) for the REW (albino) gene.

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## KazzysKritters

Also, those calculations are just for the obvious color. No clue what their parents were like, so definitely could be some other variables that are currently unknown. The current litters, and (at least) the next litter the REW female has will all be held back (except for some of the bucks, don't have space for a bunch of males unless I can get them to not try to kill each other). Maybe I'll see some other variations in the mix once they are all old enough to breed.

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## Zamwyn

* is used when you don't know what else is on that locus for the mouse in question. For example, if you have an agouti you don't know the parents of, you'd put A* (or sometimes A-) as to note that you don't know if it is homozygous for agouti AA or heterozygous Aa or Aa(t) usually. An AA mouse will give 100 % A babies no matter what you pair it with. If that's the genotype of your agouti doe, you won't get black babies even though the male is black.

True albino is cc and "conceal" all other colours. However, a red eyed white is not necessarily an albino genetically. Mice have several genes that in combination might result in a fenotypically rew. So a rew + black cross would only give all black babies if the rew is genetically aa and the two mice share no other recessive mutations.

Black + black will never give any type of A babies, but depending on possible shared recessives they might give you combination colours like blue, chocolate or dove for example. If they don't have eachother's recessives, then yes, 100 % black will be the result.


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## Lilly

One small note is that in mice it is pink eyed white, there is no red eye gene, eyes are either pink, ruby or black (and ruby is mostly associated with siamese)

With regards to the agouti calcuations,

The agouti litter could be 100% agouti, there is no way of knowing if a mouse is A/A or A/a, if she is A/a and bred to a black then the offspring will be 50% A/a 50% a/a (so agouti and black)

The reason you will sometimes see a/* is that the * indicates that you do not know what the other copy of the gene. In most cases this is because a dominant gene is showing and you don't know if its homoyygous or het.

Generally for your agouti doe, she would be coded as A/* because you do not know whether she is A/a or A/A.

The reason that you can see a/* even though a is recessive is that on that locus there is also extreme dilution (ae) which is recessive to black (supposedly but I am convinced its not entirely recessive, but thats another matter). So theoretically a black could be a/ae or a/a hence why you will see the *. Realistically you are unlikely to encouter ae in pet shop stock and it doesn't effect the black but more any fault hairs the mouse might have


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## KazzysKritters

Phew! That's a lot to figure out. Haha!

So I either have a REW or an albino with one of my girls? How can you tell the difference, if there are any physical differences? Reminds me of leopard geckos, where there are 3 known strains of albino, but they won't produce albino if the strains are mixed (just double recessive babies).

Also, I'm guessing I'd currently describe mine with asterisks seeing as I do not know of any other genes that could come into play (which I'm sure there are, as these came from a breeder that had a mix for breeding for feeders). Guess it'll be a bit of mouse lottery until I can prove everyone out! Haha

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## KazzysKritters

Whoops, sorry, didn't see your response, Lilly! I have no idea why I was typing REW instead of PEW.

So let me correct myself and say I either have a PEW female or an albino.

Should I just consider all of mine to have an asterisk, until I see what they produce? 
Male black - a/*
Female Black- a/*
Female Agouti - A/*
Female PEW - ???

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## Lilly

You can be almost certain you have albino, which is what pew is genetically in 99.9% of cases.

Which is c/c on the c locus

The blacks you can pretty much says are a/a, the chances of you having ae unless you got it specifically from a breeder are pretty slim.

The pew you will have no idea what she has on the A locus, since c/c covers everything


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## KazzysKritters

Lilly said:


> You can be almost certain you have albino, which is what pew is genetically in 99.9% of cases.
> 
> Which is c/c on the c locus
> 
> The blacks you can pretty much says are a/a, the chances of you having ae unless you got it specifically from a breeder are pretty slim.
> 
> The pew you will have no idea what she has on the A locus, since c/c covers everything


Thanks! Certainly going to be fun to see how they all turn out. Hoping I can find a local breeder so I can get some fancier mice, so I can play around with other patterns and colors.

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## Lilly

Well TN is a pretty good area as far as america goes, there was an FMBA show in Knoxville in July where quite a few TN based breeders come some stock, although mostly texels/rex (hopefully this will happen again next year too). There's also quite a few people in GA depending on where abouts in TN you are, or if you get into mice more its not too hard to get small animal transports you can hop in on for a small delivery fee to get some mice to you


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## KazzysKritters

Lilly said:


> Well TN is a pretty good area as far as america goes, there was an FMBA show in Knoxville in July where quite a few TN based breeders come some stock, although mostly texels/rex (hopefully this will happen again next year too). There's also quite a few people in GA depending on where abouts in TN you are, or if you get into mice more its not too hard to get small animal transports you can hop in on for a small delivery fee to get some mice to you


If I am able to attend that show, I certainly will! It's about 3 hours from me, so we'll see when it comes around.

There's a Repticon coming up next weekend, and there are typically other exotics vendors, including small pet vendors, at most shows like that. Maybe I'll run into someone there. If not fancy mice breeders, there will definitely be feeder mice Breeders, and I'm sure a few would have some different variations in their stock. Thinking about taking a few geckos to sell there, maybe I'll find someone willing to trade.

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## KazzysKritters

Oh, and I meant to ask. Without considering what hidden genes my mice might have, are there any other colors that I could produce with this group other than black, Agouti, and PEW?

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## Lilly

Assuming they don't have anything hidden then no, in fact first generation unless you breed pew to pew then you'd only get black and agouti.

What they carry is anyone's guess though, dove and blue are not uncommon in pet shop stock (dove is a black mouse with pink eye gene a/a p/p) so carrying those are possibilities, I think recessive yellow is pretty common too (e/e)


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## KazzysKritters

Lilly said:


> Assuming they don't have anything hidden then no, in fact first generation unless you breed pew to pew then you'd only get black and agouti.
> 
> What they carry is anyone's guess though, dove and blue are not uncommon in pet shop stock (dove is a black mouse with pink eye gene a/a p/p) so carrying those are possibilities, I think recessive yellow is pretty common too (e/e)


I need to ask the guy what else he had in his stock.

How are doves made? I'm assuming it's a black (a/a) and PEW (non-albino) (pu/pu) cross, causing hets, then the young bred together for the possibility of both black, white, doves, and PEW? Or is dove its own "morph"?

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## Lilly

Dove is simply black with two copies of the pink eye gene (which dilutes black pigment but has very little effect on yellow pigment)

Pink eye is p/p

So a dove is a/a p/p

I guess mice are a bit different to reptiles in that regard (and called varieties rather than morphs). There is no pu in mice and dove is the go to source of pink eye, being the simplest version, everything in mice is based on yellow, black or a mix of the two and dilutions thereof.

So you would either breed two blacks carrying pe for 25% dove 50% black carrying pe 25% black without the gene or a black to a dove for 50/50


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## KazzysKritters

Lilly said:


> Dove is simply black with two copies of the pink eye gene (which dilutes black pigment but has very little effect on yellow pigment)
> 
> Pink eye is p/p
> 
> So a dove is a/a p/p
> 
> I guess mice are a bit different to reptiles in that regard (and called varieties rather than morphs). There is no pu in mice and dove is the go to source of pink eye, being the simplest version, everything in mice is based on yellow, black or a mix of the two and dilutions thereof.
> 
> So you would either breed two blacks carrying pe for 25% dove 50% black carrying pe 25% black without the gene or a black to a dove for 50/50


Saw pu on some other site. Seems there are differing codes depending on the site, which is what's really messing me up. Haha!

So, if my PEW isn't albino, I could produce dove down the line eventually? Of course, I understand that the likelihood of that is slim, considering she's most likely albino. Guess we'll see!

Thanks so much for the help!

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## Lilly

The codes are almost universal but the names for things differ in a couple of cases (like dove with the AFRMA and the rest of the world), have to admit I have never seen pu before so would be interested to know where you saw it and what it was actually referring to.


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## KazzysKritters

Lilly said:


> The codes are almost universal but the names for things differ in a couple of cases (like dove with the AFRMA and the rest of the world), have to admit I have never seen pu before so would be interested to know where you saw it and what it was actually referring to.


I went back, and noticed I misread. There is a Ruby Eyed White picture, and it was classified as ru/ru. My mistake!

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## Lilly

Ah yeh, I have read about that but never actually seen someone have it, although it seems to be mostly where people have bred a dove to be very dark, choosing for darker eyes, or a very light chocolate (chocolates have been known to have ruby eyes at times) and then pied or some form of white marking, that you breed to be all over the body leaving just the eye color darker, so I am not so sure if it is actually a separate gene or just the effect of selective breeding on either pink eye gene or chocolate, just as siamese can range from looking pew to having eyes so dark they're almost black, but genetically it is always a black eyed mouse underneath.

Sorry guess that is a bit off topic, I tend to waffle on because I love genetics! lol


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## KazzysKritters

Lilly said:


> Ah yeh, I have read about that but never actually seen someone have it, although it seems to be mostly where people have bred a dove to be very dark, choosing for darker eyes, or a very light chocolate (chocolates have been known to have ruby eyes at times) and then pied or some form of white marking, that you breed to be all over the body leaving just the eye color darker, so I am not so sure if it is actually a separate gene or just the effect of selective breeding on either pink eye gene or chocolate, just as siamese can range from looking pew to having eyes so dark they're almost black, but genetically it is always a black eyed mouse underneath.
> 
> Sorry guess that is a bit off topic, I tend to waffle on because I love genetics! lol


Haha, it's cool! I love learning about genetics.

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## PPVallhunds

I once did a post that may help you on the thread below. It's explains the diffrent groups of gene and what effect that have when combined with other colour genes.

viewtopic.php?f=26&t=34458&hilit=Idiot


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## KazzysKritters

PPVallhunds said:


> I once did a post that may help you on the thread below. It's explains the diffrent groups of gene and what effect that have when combined with other colour genes.
> 
> viewtopic.php?f=26&t=34458&hilit=Idiot


Thanks so much! I'll check it out now 

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