It is common misconception that the "Pintabian" (pin-TAY-bee-an) horse is simply a cross between an Arabian and a spotted horse of Pinto or
Paint breeding. This, however, is not the case.
Because of its dominant characteristics, experts in the field of genetics have known for years that it is possible to breed the popular tobiano
spotting pattern into the Arabian breed to produce a "relatively pure" strain of tobiano horses with over 99% Arabian blood (also known as the
Pintabian!). As you may already know, the purebred Arabian horse does not come in the tobiano pattern. Also, because of the genetic make-up of
the tobiano gene, at least one parent must be a tobiano in order to produce a horse with tobiano markings. The Pintabian breed was developed
by continually crossing tobianos back to purebred Arabians, and in order to be eligible for registration in the Pintabian Horse Registry, horses
must be  99.2% Arabian in blood.

Here's how it works:
1/2 Arabian = 50% Arabian in blood

3/4 Arabian = 75% Arabian in blood

7/8 Arabian = 87.5% Arabian in blood

15/16 Arabian = 93.75% Arabian in blood

31/32 Arabian = 96.875% Arabian in blood

63/64 Arabian= 98.4375% Arabian in blood

127/128 Arabian = 99.21875% Arabian in blood (Pintabian!)
(and so on)
But what does the fraction 127/128 really mean?
A horse that is 1/2 Arabian usually has one parent that is Arabian and one that is not (1 out of 2 parents are purebred Arabian). A 3/4 Arabian
usually has three purebred Arabian grandparents and one that is not (3 out of 4 horses in the second generation are purebred Arabian).
Similarly, of the 128 ancestors in the seventh generation of a Pintabian's pedigree, 127 were purebred Arabian. Only one was not. The horse that
was not a purebred Arabian, by the way, is the one that contributed the tobiano pattern.
It is because of this high degree of Arabian blood that the Arabian "type" of the Pintabian horse breeds true.

To quickly determine the amount of Arabian blood, add the blood percent of the stallion to the percent of Arab blood in the mare and divide by
two. This manipulation of blood factoring differentiates the Pintabian from the other coloured horse registries.
What is a True Pintabian Horse