Scientists have discovered how cats and some horses get distinctive piebald patches - and it could prevent serious health defects.
Defective versions of a gene called 'kit' reduce the rate at which cells multiply, giving the animal a white tummy because there are too few of them to cover the whole body.
Their findings debunk an existing theory that patches form because pigment cells move too slowly to reach all parts of the developing embryo.
Researchers at the Universities of Bath and Edinburgh, who carried out the study, say the way that black and white patches develop on unborn kittens could improve understanding of some congenital health conditions linked to early cell positioning.
For example, holes in the heart are caused by cells not moving to the right place as an embryo develops, in a similar process which gives some cats their distinctive black and white patches.
The study is published in the journal Nature Communications.