# Black tan genetics help!



## Kallan (Aug 16, 2009)

Howdy! I'm tying my brain in knots trying to work out the genetics of two of my meeces.

One is Ecclie:









Ecclie is a black tan, so either a_t_/a_t_ or a_t_/a. I'm assuming he could have other recessive genes on other loci, but because they are recessive they don't affect his appearance.

Next is Astrid:









When crossed the two produced:
6/11 Black tan broken
2/11 Black broken (suggesting at least one parent is hetero a_t_/a)
2/11 Pale greyish with much lighter undersides, broken - diluted tans?
1/11 Brown broken (Poorly variegated?):









Ok, so questions:
Astrid was broken black tan. So again, a_t_/a_t_ or a_t_/a. With her brokenness, will she be s/s, or W/w? All her offspring were broken, which would suggest a capital letter in there somewhere, therefore W/w, or am I totally on the wrong track?

Brown broken with black parents - that the brown gene or the extreme dilution gene?

How does at/a work if neither are dominant?

thanks to anyone who can help, I have 5 notebook pages so far of test genetic crosses to work out the proportions!


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## Jack Garcia (Oct 9, 2009)

The daddy has a white spot around his belly. That's suggestive of variegated (a dominant trait), to me. I've seen it in a lot of "poor" variegated mice. But it can also be indicative of banded (another dominant trait), or recessive white spotting (aka "broken" or "even").

Tan, at, _is_ dominant to a, just not to A. 

I'm glad somebody else keeps a notebook with mouse breeding notes in it. I don't feel so lonely.


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## Kallan (Aug 16, 2009)

There is one other mouselet who looks poorly variegated - the rest have big blotches with fairly clear borders. Could that be variegated still?


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## Jack Garcia (Oct 9, 2009)

Yeah, the thing about variegated and banded is that they both can produce mice that look a bunch of different ways, from nearly solid colored (self) to nearly white, to a mouse who has spots evenly distributed "correctly" to any number of extremes. That's part of the reason breeding marked varieties for show is so difficult (in my humble opinion). 

And depending on the individual mice and their families, sometimes you know you have a dominant marking gene at play, but you don't know which one.


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## Cait (Oct 3, 2008)

I am pretty sure they're broken (s/s). Variegated isn't common outside showing circles (and not that common in them either really), and would have some suggestion of splashing, which I cannot see in your mouse. If two tan parents produced even one mouse that is not tan, they must both be heterozygous for tan (so that the baby could be a/a since at is dominant to a).


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