Did you know that Jacobs and Black Welsh Mountain sheep are unique in the fact they are dominantly black genetically? I knew Jacobs were, but I didn’t know there were only two breeds of sheep like this. All other breeds must either be colored or have a recessive colored gene to throw colored offspring.
This is what a typical Jacob cross looks like. Mostly black with splashes of white, usually on the head.
My sister bought a few sheep from us a couple years ago – a Jacob ram and a some crossbred ewes. Imagine my surprise when she sent me this picture…
The dad was a purebred Jacob and the mom was a Jacob x Bluefaced Leicester. Not only is he Jacob looking, but he is also lilac colored. We expected her lamb to look like her – black with a bit of white.
Everytime I think I understand this breed, even just a little bit – something like this happens.
Stories from the Farm 
My understanding is that the extension gene is present in Jacobs, and it has entered the Shetland breed and many others as well.
UM there are actual several breeds that carry the dominant black allele, Karakul, Black Welsh Mountain, Shetland, Icelandic, Jacob and some of the other middle eastern breeds all have the dominant black genes.
I’m sorry for posting inaccurate information. Thank you for the correction. I know very little when it comes to color genetics and I rely on information I have read. Since posting this I have learned that Shetlands and Icelandics carry the dominant black allele and now Karakul as well. Someone said that they have discovered that the dominant black allele found in Black Welsh Mountain came from the Jacob sheep a very long time ago – do you know if this is correct?