Question about the genetics of colour

[TeresaA]

The woman who I bought my horse from forwarded an email about her colour genetics:

She is Gg (heterozygous for grey) meaning she has a 50% chance of producing a grey foal no matter what the base color is

BB, (homozygous dominant black) means she carries 2 dominant genes for producing black pigment

AA (homozygous dominant agouti) meaning the distribution of the black pigment will be at the extremities, i.e. a BAY coloring pattern

She does not carry the red gene and should not be able to produce a chestnut even if bred to one.

The black gene is confusing, she will not produce a true black foal, only shades of bay.

Therefore all of her foals born should be bay, except for the 50% that will fade to grey. Hopefully that makes sense. I’m not sure now the dilution/cream genes work, and we did not test for those alleles since she did not have any ancestors that were dilute colors.

The genetics of colour is new to me so I have a question: If I breed her to a Bay stallion that I have my eyes on, does that increase the chances of getting a bay?

And just for fun here's a photo of her:

[Chisamba]

My understanding is you will get a foal born bay who has fifty percent chance of greying.

If you want a bay you'll probably get grey

Such a lovely photo

[Kelo]

Chisamba is correct. Think of gray as an overlay. So mentally remove the gray and use the base color to calculate percentage of color. In your case, bay. Then no matter what the base color result is, you then add a 50/50 chance of getting gray.

If you bred her to a cream dilute -- like, say, a cremello or perlino -- you'd have a 100% chance of getting a buckskin....which would then have a 50/50 chance of turning gray.

[TeresaA]

Thank you! I would really really love a bay colt so would likely get a grey filly.

Not breeding her this year but it is in my mind. She's very well bred and nicely put together.

Kilo now has me thinking of a buckskin.....