Mamma Mia said:
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I was reading somewhere -maybe here - that linking the grey DNA test to the overall genome of the horse reveals that all grey horses descended from one common ancestor
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Hi MM, I posted on this recently:
Grey horses are all related! Breaking (genetics) News
In the original paper from Nature Genetics, greying is thought to be due to overexpression of one or two genes (NR4A3 and/or STX17), which promote melanocyte proliferation. NR4A3 is linked with cell cycle regulation (and carcinogenesis). They believe STX17 duplication leads to overgrowth of skin melanocytes and thus melanomas. However the excess growth in the hair-follicle melanocytes depletes the stem cells...leading to premature greying. This theory is supported by the fact young grey horses darken before onset of greying.
I hope that makes some sense!!