Red Unders genes all attach to the same area, creating a series. Creatures can only have two genes in a series at most, one inherited from each parent.
So they could, for example, be PtWU (or) PtPt (but not) PtPt WU. They could also be nn for the series, and have no markings here.
Red Unders genes are codominant, meaning having more than one different type will show the effects of both.
However, having duplicates, like two copies of Pt, will not create two different types of Points.
Red based, affected by any genes that target red, such as axanthic
Underbelly countershading which can range anywhere from a light brown, to cream, to so pale it appears white, but is always lighter than the base coat
May have gaps, especially around the neck
May spread up to ears and cover most of the face
Usually starts as four inside socks, can spread up body and create various strips on the legs, rump, and face.
Can impact only part of the underbelly, such as the rump or inside of legs
May have a slight gradient.
Skin is not affected. Eyes are not affected.
In hooved creatures, mane and tail may be white where marking touches.
Compare to: Countershaded animals such as Bengal Tiger, Lion, Gemsbok, Blackbuck, Blesbok, Pronghorn, Whitetail Deer