# How do genetics work?



## Demi (Feb 14, 2009)

I've looked at the lists of codes,but I don't understand how that makes the colour of a baby mouse?? :?:


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## ian (Oct 3, 2008)

The letters in the codes refer to different groups of genes.
The important groups are: 
A, B, C ,D and P
Each mouse has two genes in each group, one from each parent.
Wild mice are agoutis and they have the code AA BB CC DD PP which is the basic genetic make up of all mice. So in order to make the mouse a different colour you need to introduce a different gene.

So with the A group
A is agouti 
a is black

because the agouti gene is shown as a capital 'A' it means it is a dominant gene. This means that if the mouse has got an agouti parent and a black parent it will have the code 'Aa' so although it has one black gene the agouti gene is stronger and the mouse will be an agouti. To be a black it would have to have a little 'a' from both parents and its code would be 'aa'.

Other colours which we commonly see are caused by dilution genes, these are all recessive means they are like the black gene 'a' and need to get one of each from both parents.

The B group controls whether the mouse is chocolate.
chocolate is 'b' so a chocolate mouse needs to have a 'b' from each parent. The 'B' gene has no effect on colour so if a mouse is 'BB' its colour will be decided by other genes. If it is 'bb' then it will be chocolate.

The C group is very complicated and has various genes which can make a mouse albino, cream, silver and others.

The D group talks about mice being Blue and works in exactly the same way as the chocolate gene.

The P group controls eye colour. 
'P' is black eyes
'p' is pink eyes.

If a mouse has pink eyes it sometimes has the effect of making the fur colour lighter too. So two mice can have exactly the same code until it gets to the P group and they can look entirely different. For example
aa BB CC DD PP-is a black
aa BB CC DD pp-is a dove

Another gene that is very important is 't' for tan. It has a little 't' but its actually dominant so the mouse only needs to have one tan gene from either parent and it will have a tan on the belly.

Other genes particularly those genes that cause markings work in their own ways and I find it easiest to look these up as and when you need them, theres no point learning all of the genes as you might never have a mouse which has these genes.
I hope that is a little bit clear, I just read over it and Im not sure that it is. Sorry

What genes in particular are you interested in. And what mice are you breeding/aiming to produce?


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## Demi (Feb 14, 2009)

Ohhh it makes sense now  I don't know which mice I'd want to breed coz theyre all cute


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## ian (Oct 3, 2008)

I suppose it depends whether you want to breed to show or breed good quality pets. With pet breeding ti opens you up to a much wider range of genetics and lots of colours and types which must be interesting. Show breeding is difficult, you are generally recommended to cull any mice not up to scratch, and you get lots which just arent good enough!

Hope you find the perfect variety for you, good luck.


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## Demi (Feb 14, 2009)

I think I'd only breed for pets.There is hardly anyone in durham that can find mice so it would be good to have a mousery here.


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## yyoung (Mar 30, 2009)

Thanks for that easy to understand genetics lesson. I think I am getting a bit more each time. I have a question though...

When you say about the 't' gene being dominant and only needing one from either parent to produce a tan belly....does that mean if the mother or father is tan bellied that all of the offspring will be too. It's just if that is the case then I got a mouse from pet shop (black and tan) and she was pregnant and had 7 babies. 2 of the 7 do not have tan bellies.

I have probably not 'quite got it' but I just wondered...


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## stace_m (Feb 23, 2009)

When learning about genetics I found this web site to be very helpfull and easy to read and understand.
www.thefunmouse.com 
I hope this helps


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## sommy (Mar 1, 2009)

Ian, I read over your 'ESSAY!!' a couple of times and it has really helped! merci!


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## Peteyandthegang (Jan 20, 2009)

ian said:


> The letters in the codes refer to different groups of genes.
> The important groups are:
> A, B, C ,D and P
> Each mouse has two genes in each group, one from each parent.
> ...


Thanx, that was a realy good read!


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## Cait (Oct 3, 2008)

yyoung said:


> Thanks for that easy to understand genetics lesson. I think I am getting a bit more each time. I have a question though...
> 
> When you say about the 't' gene being dominant and only needing one from either parent to produce a tan belly....does that mean if the mother or father is tan bellied that all of the offspring will be too. It's just if that is the case then I got a mouse from pet shop (black and tan) and she was pregnant and had 7 babies. 2 of the 7 do not have tan bellies.
> 
> I have probably not 'quite got it' but I just wondered...


Tan is dominant to self so it only needs one copy to show up. Therefore your tan doe has only got one copy of the tan gene and the babies who are not tan inherited the other gene along with one from their father.


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