Dominant color?

[Canis-Lupess]

In border collies, the black and white gene is most dominant.

Still, even if both parents are black and white, they can still throw coloured pups. This is because they can be heterozygus black/red for example meaning they are black and white but also carry a hidden red gene. If both parents carry a hidden recessive gene and a pup inherits the recessive coloured gene from both parents, they can come out as coloured.

The only colour in Borders where it works differently is the merle gene. This is a mutant gene and can occur even when one of the parents is homozygus black meaning they only carry black genes.

Our Jess is homozygus black and white but when mated to a tri-merle dog, she thew pups with the merle colouration but no tan like what the sire had. The tan gene was recessive so didn't come out against her dominant black genes but the merle gene being a mutant gene did come out.
When she was mated to a red tri, all pups were black and white.

One thing I also noted with the merle pups is that they were all very white factored with only merle heads and a small amount of merle on the body.
I know that Jess likely carried a gene for white factoring because some of her siblings came out that way. It either came From Jess's mother mist, or her father, Monty. Jess, Monty and Mist were all traditionally marked and even though Jess had white factored siblings, the first two dogs she was mated to produced pups from traditionally marked to minimal white markings and mainly black but when we put her to the Merle, more than half the litter were very white factored, even more white factored than her siblings before and all the merles turned out this way.
It's funny how certain genes can associate themselves with each other.

I've never known for the genes being determined by sex really. It just all depends on what genes the pups inherit from their parents.

The only sex determined colour I can think of is cats with the tortioseshell (calico) colouration. Only females are tortoiseshell because the third colour gene required to make this colouration is found on the extra strand of chromosomes that male cats don't have so males turn out either black and white or ginger tabby.

[DrKym]

All calico (tortoiseshell) cats are female??
while the vast majority of calico cats are female, there is the occasional male. However, virtually all of these males are sterile. the calico colour is sex linked. For a cat to be calico it must have two X chromosomes ergo the cat is female. In rare instances however a male calico will be produced. This usually happens because the cat has an extra chromosome. So, instead of him being XY, he is XXY. These cats are known as Kleinfelter males.

* Approximately 1-3,000 calico's are male & out of those only 1-10,000 are fertile.

and yes there are Orange females too! lol

[Canis-Lupess]

Yes, I've known of orange females although most ginger tabbies I have known are male.

I have read in some places that the very occasional male can turn out tortoiseshell then other places say only females are that colour. Still, unless the male is defective in the fact that he has an extra X chromosome, then he wouldn't be tortoiseshell. Hence most of them being sterile, I suppose.

[Giselle]

Hmm. I actually learned that calico cats are colored such not because the calico coloration is on an X chromosome but that to achieve genetic balance, one of the X chromosomes is inactivated (mosaic effect of maternal/paternal genes). Because male cats are XY, I was taught the dominant gene always overrides the recessive so there is no mosaic effect or calico coloring. But, as the stats show, there's always mutations!