# Basic Mouse Genetic Notations



## Apache (Jul 23, 2014)

Hello.

I have been breeding gerbils for some time and have got my head totally around it - but then I started reading about mouse genetics and I feel back at square 1!

Mainly I am having trouble with your notations for the different genes and was wondering how it all translates into English.

For example, your genetics showing for an Agouti mouse is A* B* C* D* P*.

Now I completely understand how this one works; but then you say Lethal Yellow is just: Ay?

Does this mean that the other genes don't matter and it over-rides them all - so if an Agouti mouse get one Ay gene it just hides all the agouti signs and displays as a yellow?

Please elaborate for me...


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## SarahY (Nov 6, 2008)

Ay is dominant over agouti, so the hair shafts lose the agouti banding and are solid red/yellow. Well, ideally, anyway! Red suffers from sootiness, where the tip of the hair is dark brown, but when selectively bred reds are a self, the same colour all the way down the hair. Only certain genes affect red; chocolate has no visual effect but blue will dilute red to a buff-gold colour. C-dilutes reduce red further to white in most cases, or yellowy cream.

In addition to Ay there is "at", tan. A/at is agouti tan, a/at and at/at are black tan, and Ay/at is a sable.

As you have a genetics knowledge, I'm sure the Finnmouse site will tell you all you need about mouse genetics:

Genetics information: http://hiiret.fi/eng/breeding/?pg=5
Varieties information: http://hiiret.fi/eng/breeding/?pg=4


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## Apache (Jul 23, 2014)

Thank you. And I will have a good read of your links

But, basically you are saying that the Ay makes the agouti coat turn solid/self red; and by having homozygous recessive blue genes in the mix, you get the red to fade to a yellow colour?

Also, this 'lethal yellow' yellow gerbil is apparently prone to many health issues - is it 'lethal' in all mice with Ay, or only when you fade them to yellow with the blue effect?

And finally, your C genes work differently to gerbils - so when you said that 'C-' helps to dilute the red further, did you mean dominant C itself or were you referring C plus any of the lesser c genes (so Cc, Cch, Cce or Ccch)?

Thank you so much for your help.


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## SarahY (Nov 6, 2008)

Yes, Ay/A is a self mouse. Lethal yellow mice are prone to obesity, but otherwise are as healthy as any other varieties. Ay is called lethal yellow because it is a lethal homozygous and AyAy mice die early in foetal development.

With the c-dilutes, they are all recessive. CC or Cc, Cch, Cce, Ccch are all full colour.


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## Apache (Jul 23, 2014)

Ok, so all your little c's are recessive - but which combination would be best at fading out the red colour to a yellow colour?

In gerbils they only have the c(chm) chinchilla medium (burmese) and the c(h) himalayan. The c genes - even when with a dominant C - can fade the coat colour (lilac becomes sapphire with Cc(chm) and then fades to Dove with Cc(h)) - and 2 c(h)'s together bleaches out ALL colour - even at the points.

Would any of your mouse c's have a total bleaching effect? And if you had to scale their fading effect - what order would you put your 4 c's into?


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## SarahY (Nov 6, 2008)

The mouse c-dilutes are c - albino, ce - extreme dilution (dilutes all pigment except the eyes), ch - Himalayan/Siamese, cch - chinchilla (dilutes red pigment only). There are other c-dilutes recorded, but these are the ones that exist in the fancy. All of the c-dilutes have a drastic effect on red pigment, some have little or no effect on black pigment.

Ay/* c/c = albino (pink eyed white)
Ay/* c/ce = black eyed white
Ay/* ce/ce = black eyed off-white
Ay/* c/ch = pink eyed white
Ay/* ch/ch = ruby eyed white
Ay/* ce/ch = black eyed off-white
Ay/* c/cch = black eyed off-white
Ay/* cch/cch = black eyed yellow-cream. 
And blue - Ay/* C/* d/d = black eyed yellow.

Compared with an agouti or black base rather than red:

a/a c/c = albino (pink eyed white)
a/a c/ce = black eyed cream (bone in Europe)
a/a ce/ce = stone (beige in Europe and the US)
a/a c/ch = Himalayan
a/a ch/ch = Siamese
a/a ce/ch = black eyed Siamese (colourpoint beige in Europe and US)
a/a c/cch = brown
A/* c/cch = pale, browny chinchilla colour
a/a cch/cch = just off black (a/at or at/at is black fox)
A/* cch/cch = silver agouti (A/at or Aw/* cch/cch is chinchilla)
a/a ch/cch = burmese (sable Siamese in the US)
a/a ce/cch = brown
A/* ce/cch = browny chinchilla colour

Adding the pink eye dilute gene (p) changes the black eyed to pink eyed, so Ay/* ce/ce p/p = pink eyed off-white and Ay/* cch/cch p/p = pink eyed yellow-cream.

The dominant yellow and tan gene gives the sable varieties:

Ay/at = sable
Ay/at cch/cch = marten sable

Pale, poor marten sables can be made with Ay/at ce/ce, all other combinations are white or off white, sometimes with a pale beige streak along the spine.

Heterozygous c-dilutes have no real effect on the colour, c-dilutes in mice are all true recessives.


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## Apache (Jul 23, 2014)

Wow!

Thank you so much for taking the time to write all that - it certainly all makes more sense now. All falling into place....

(and sable mice look adorable!)


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## Apache (Jul 23, 2014)

Me again quickly - about red-eye dilution.

From your lovely list above, are you saying that c and ch either in any combination fade the eyes to red even if genetically they are dark-eyed?

Basically could a Himalayan or Siamese have P/* but show red eyes? So does only breeding tell you the genetics here or can you see which are pink-eye and which are c/ch diluted?

Thanks...


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## SarahY (Nov 6, 2008)

Yes, c/ch P/* and ch/ch P/* have red eyes because they are really a kind of albino. A mouse that is c/ch p/p or ch/ch p/p looks like a pink eyed white, so you would need to test breed to tell c/ch p/p and ch/ch p/p from an albino a/a c/c.


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## Apache (Jul 23, 2014)

Thanks - but what is the best colour to breed to to find this out? It would have to be a C/C (or C/*) pink eye wouldn't it - the C to dominate over the c-recessives and the pink eyes to expose a P?


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